Ban Chiang, Northeast Thailand, Volume 2C: The Metal Remains in Regional Context 9781934536995

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BAN CHIANG, NORTHEAST THAILAND, VOLUME 2C: THE METAL REMAINS IN REGIONAL CONTEXT

Founder’s burial from Nil Kham Haeng in the Khao Wong Prachan Valley, Lopburi Province, central Thailand dating ca. mid-1st millennium B.C. Among the grave goods of this adult male burial were the disassembled sections of a complete furnace chimney by his right knee. Typical copper-base cordiform implements near the head were most probably cast on site. (Burial 1 from Operation 4 of TAP’90)

thai archaeology monograph series Series editor, Joyce C. White

Pietrusewsky, Michael, and Michele Toomay Douglas Ban Chiang, A Prehistoric Village Site in Northeast Thailand I: The Human Skeletal Remains, 2002. White, Joyce C., and Elizabeth G. Hamilton, editors Ban Chiang, Northeast Thailand, 2A: Background to the Study of the Metal Remains, 2018. White, Joyce C., and Elizabeth G. Hamilton, editors Ban Chiang, Northeast Thailand, 2B: Metals and Related Evidence from Ban Chiang, Ban Tong, Ban Phak Top, and Don Klang, 2018. White, Joyce C., and Elizabeth G. Hamilton, editors Ban Chiang, Northeast Thailand, 2C: The Metal Remains in Regional Context, 2019. White, Joyce C., and Elizabeth G. Hamilton, editors Ban Chiang, Northeast Thailand, 2D: Catalogs for Metals and Related Remains from Ban Chiang, Ban Tong, Ban Phak Top, and Don Klang, forthcoming.

University Museum Monograph 153

BAN CHIANG, NORTHEAST THAILAND, VOLUME 2C: THE METAL REMAINS IN REGIONAL CONTEXT

Joyce C. White and Elizabeth G. Hamilton, editors

university of pennsylvania museum of archaeology and anthropology philadelphia

library of congress cataloging-in-publication data Names: White, Joyce C., 1952- editor. | Hamilton, Elizabeth G. (Elizabeth Garrett), editor. Title: Ban Chiang, northeast Thailand. Volume 2C, The metal remains in regional context / Joyce C. White and Elizabeth G. Hamilton, editors. Other titles: Volume 2C, The metal remains in regional context Description: Philadelphia : University of Pennsylvania Museum of Archaeology and Anthropology, 2019. | Series: University museum monograph ; 153 | Includes bibliographical references and index. Identifiers: LCCN 2019025980 | ISBN 9781931707930 (hardcover) | ISBN 9781934536995 (ebook) Subjects: LCSH: Prehistoric peoples--Thailand--Ban Chiang (Udon Thani) | Metal-work, Prehistoric--Thailand--Ban Chiang (Udon Thani) | Ban Chiang (Udon Thani, Thailand)--Antiquities. Classification: LCC GN778.32.T5 B362 2019 | DDC 959.3/021--dc23 LC record available at https://lccn.loc.gov/2019025980

© 2019 by the University of Pennsylvania Museum of Archaeology and Anthropology Philadelphia, PA All rights reserved. Published 2019 Distributed for the University of Pennsylvania Museum of Archaeology and Anthropology by the University of Pennsylvania Press. Printed in the United States of America on acid-free paper.

dedication This volume is dedicated to Helena Kolenda, Program Director for Asia at the Henry Luce Foundation, and Leslie Kruhly, Vice President and Secretary of the University of Pennsylvania and former Development Director of the Penn Museum. We are deeply grateful for their unceasing encouragement and belief in us and our work, and for their strategic assistance in the continuation of the Ban Chiang Project at the Penn Museum. Their support made the preparation of the monograph suite on Ban Chiang metallurgy possible.

Contents

list of figures list of tables contributors 1

x xii xiii



providing a regional socioeconomic context for prehistoric metallurgy in thailand

Joyce C. White

1

2

prehistoric copper mining and smelting in southeast asia: evidence from thailand and laos

5



3

Vincent C. Pigott

Introduction Three Locations with Copper Production Evidence Ore Sources and Early Mining and Exploitation Northeast Thailand: The Greater Loei Region The Phu Lon Complex: Mining and Smelting The Phu Lon Complex in Regional Context Central Thailand: The Lopburi Region Non Pa Wai Nil Kham Haeng Non Mak La Metallurgical Activity in the Khao Sai On Mineral District Sepon, Laos–A Multi-site, Prehistoric, Mining and Smelting Complex Khanong A2 Tengkham South D Concluding Observations

lead isotope characterization and provenance of copper-base artifacts from ban chiang and don klang

T. O. Pryce

Methodology Results Discussion Conclusion

5 6 7 8 8 20 22 25 37 44 47 50 51 51 53

57 58 58 62 63

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4

5

6

CONTENTS

the archaeometallurgy of prehistoric northern northeast thailand in regional context 65

Elizabeth G. Hamilton and Joyce C. White

Introduction Note on a Regional Relative Sequence Metal-consuming Sites in Northern Northeast Thailand Sakon Nakhon Basin Sites Upper Nam Phong Watershed Sites Phetchabun Range/Piedmont Sites East Mekong Metal-consuming Sites in Southern Northeast Thailand Middle Chi Valley Upper Mun Valley Metal-consuming Sites in Central Thailand Ban Don Ta Phet Nong Nor Ban Mai Chaimongkol Other Central Thai Consumer Sites Summary of Central Thailand Metal Consumption

a regional synthesis of early metal technological systems in prehistoric northeast and central thailand

Joyce C. White and Elizabeth G. Hamilton

65 75 75 76 83 92 94 96 96 97 114 114 117 118 118 120

123

Early Metal Technological Systems 124 Earliest Metal Production 124 Manufacturing Copper-base Finished Products 130 Alloy Developments 138 Regional Variations and Networks 141 Iron 143 Initial Appearance 143 Middle Iron Period 143 Bimetallism 144 Transmission 144 Assemblage Variation 144 Iron Technology 146 Social Contexts of Metallurgy 147 Founder’s Burials 148 Consumer Burials in the Bronze Period 150 Iron Period Social Context 151 Summary 152

conclusions: placing metals in social contexts in prehistoric thailand

155

Early Metallurgy in a Resource-rich Region Distinctive Social Context Related to Ore Proximity?

156 156

Joyce C. White

CONTENTS

Socioeconomic Overview Organization of Copper Production Manufacturing of Metal Objects Consumer Demand Consumer-producer Relationships Distribution and Ricardo’s Law Transmission and Adoption Prospective Outlook Future Studies in Mainland Southeast Asia Paths Forward Southeast Asia’s Contribution to Archaeometallurgy

references index

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157 158 159 161 164 167 169 170 170 176 182 184 210

Figures (color insert appears between pages 130 and 131)

1.1 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10a 2.10b 2.11 2.12 2.13 2.14 2.15 2.16a 2.16b 2.17 2.18 2.19 2.20 2.21

Founder’s burial from Nil Kham Haeng Provinces of Thailand and Laos Schematic diagram of the location of the hills/orebodies of Phu Lon I and II Contour map of the mining locations of Phu Lon I Phu Lon Mining Complex 14C dates Distance view looking southeast at hill of Phu Lon I Schematic diagram of the weathered copper sulfide orebody at Phu Lon I Stone mining maul made from a local igneous river cobble View of the Pinnacle View of Udom’s Rock with vestiges of mining pits on its surface Sinuous mine shaft sunk in the base of the Pinnacle at Phu Lon I Profile view of the Pottery Flat stratum of crushed copper ore and host rock Close-up of the Pottery Flat stratum of crushed copper ore and host rock View looking south across the Pottery Flat Large stone anvil from the surface of Phu Lon II Fragment of a sandstone bivalve mold half for the casting of a small socketed implement Map of the Lopburi Region metal extraction sites discussed View of typical stratigraphic profile at Non Pa Wai The so-called “Grave of the Metalworker” from Non Pa Wai Broken but complete ceramic bivalve adze/axe mold pair from the “Grave of the Metalworker” The range of typological variability in ceramic cup and conical ingot-casting molds Examples of marked ceramic bivalve mold halves from Non Pa Wai and Nil Kham Haeng A marked ceramic thick-butted, shallow mold Side and top views of typical ceramic smelting crucible from Non Pa Wai A typical ceramic perforated chimney from an iron period burial at Nil Kham Haeng

Frontispiece 3 9 10 11 Color insert 13 15 Color insert Color insert 15 17 17 17 Color insert 20 23 Color insert Color insert 28 29 Color insert 29 Color insert Color insert

FIGURES

2.22a Typical surface find example of a plano-convex slag cake from Non Pa Wai 2.22b Cross section through slag cake from Non Pa Wai 2.23a Typical ceramic cup mold for casting a copper ingot from Non Pa Wai 2.23b A slag ingot pseudomorph from iron period Non Pa Wai 2.24 Ingot resulting from an experimental casting at a local foundry in Lopburi 2.25 Top and side views of a ceramic mold plug from Non Pa Wai 2.26 Two cast copper-base ingots excavated at Non Mak La 2.27 Stratigraphic profile from the mound of Nil Kham Haeng 2.28 Group of copper-base cordiform artifacts from iron period burials at Nil Kham Haeng 2.29 Hypothesized reconstruction of a smelting installation used at Khok Din and Noen Din 2.30 Hypothesized reconstruction of a smelting crucible from Khok Din and Noen Din 3.1 Lead isotope plot comparing ratios for Phu Lon, Sepon, the Khao Wong Prachan Valley (KWPV), Ban Chiang, and Don Klang 3.2 Magnified view of the area of Fig. 3.1 where numerous samples overlap 4.1 Map of metal age sites discussed in the chapter 4.2 Plan and section of a copper-base casting hearth from Level 7 at Ban Na Di 4.3 Tin bronze socketed adze (NNT-152) from Early Period Non Nok Tha 4.4 Tin bronze bar from Ban Mai Chaimongkol bronze period 4.5 Ban Non Wat socketed adze/axe from phase BA2 Burial 290 4.6 Socketed adze from the basal bronze period layer at Non Pa Wai

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31 Color insert 33 33 34 35 36 Color insert Color insert 49 Color insert Color insert Color insert 66 78 87 105 107 120

Tables (foldout appears between pages 130 and 131)

2.1 Radiocarbon Determinations from Phu Lon 2.2 Working Chronology for the Khao Wong Prachan Valley and the Khao Sai On Mineral District Sites 2.3 Evidence for Metal Activities at the Phu Lon Complex, Three Sites in the Khao Wong Prachan Valley, and Three Sites in the Khao Sai On Mineral District 3.1 Artifacts from Ban Chiang and Don Klang Selected for Lead Isotope Analysis 3.2 Elemental Compositions of the Artifacts Selected for Lead Isotope Analysis 3.3 Lead Isotope Ratios for Artifacts from Ban Chiang and Don Klang 4.1 Prehistoric Metallurgical Evidence Found in Metal-consuming Sites in Northeast and Central Thailand 4.2 Archaeometallurgical Research on Prehistoric Metal-consuming Thai Sites 4.3 Regional Temporal Units in Relation to Ban Chiang Periodization 4.4 Regional Chronological Sequences 4.5 Approximate Summary Correlation of Ban Na Di Levels and Ban Chiang Periods and Burial Phases

12 24 26 59 60 61 67 73 75 Foldout 77

Contributors

Joyce C. White received her Ph.D. in Anthropology in 1986 from the University of Pennsylvania, with a dissertation on the chronology of Ban Chiang. She has been Director of the Penn Museum’s Ban Chiang Project since 1982 as well as a Senior Research Scientist and Associate Curator for Asia at the Museum, before founding and becoming the Executive Director of the Institute for Southeast Asian Archaeology in 2013. She is also currently an Adjunct Professor in Penn’s Department of Anthropology and a Consulting Scholar at the Penn Museum, where she continues her lifelong passion to foster scholarship of the prehistory of Southeast Asia with special emphasis on Thailand and now Laos. Joyce C. White Executive Director Institute for Southeast Asian Archaeology 3260 South St. Philadelphia, PA 19104-6324 [email protected] Elizabeth G. Hamilton received her Ph.D. in Anthropology from the University of Pennsylvania in 1995, with a dissertation on the development of the copper-working industry in late Iron Age and Roman Period Gaul. She has been working on the analysis of Southeast Asian metals since 1999. She is currently a Research Associate at the Institute for Southeast Asian Archaeology and a Consulting Scholar at the Penn Museum. Elizabeth G. Hamilton ISEAA/Ban Chiang [email protected]

James D. Muhly studied Classics and Ancient History, receiving his B.A. from the University of Minnesota in 1958. He was awarded a Ph.D. from Yale University in Assyriology and Near Eastern Archaeology in 1969. He taught at the University of Minnesota from 1964 to 1967, moving to the University of Pennsylvania in 1967. He retired as Professor Emeritus from the University of Pennsylvania in 1997, serving as Director of the American School of Classical Studies at Athens from 1997 to 2002. James has taught and published widely on various aspects of the history and archaeology of the Aegean and Near East, with special emphasis on metallurgy. He is currently studying the metal objects of the Petras cemetery. His Foreword to the Ban Chiang metals study is found in TAM 2A. James D. Muhly Proteos 36 Palio Faliron, Athens 175 61, Greece Samuel K. Nash received his Sc.D. in Metallurgy from the Massachusetts Institute of Technology in 1951. After 26 years as a physical metallurgist attached to the US Army Frankford Arsenal, he retired as the Chief of the Metals Engineering Branch. From 1953–1995, he served as Adjunct Professor and then Lecturer in Materials Science at Drexel University. After his retirement, he volunteered as a metallurgist at MASCA, the Penn Museum’s former Museum Applied Science Center for Archaeology, and in 2009 became a Consulting Scholar at the Museum. He retired from the Museum in 2016. Samuel Nash co-authored with Elizabeth Hamilton

CONTRIBUTORS

the metallographic and elemental analyses presented in TAM 2B, chapter 4. Samuel K. Nash 1420 Locust St.--9A Philadelphia, PA 19102 †William W. Vernon received his Ph.D. in Geology from Lehigh University in 1964 and an M.S. in Anthropology from the University of Pennsylvania in 1984. He specialized in the analysis of minerals, rocks, and ceramics using microscopic methods. He was co-director of Archaeological Excavations in NY State from 1972–1980 and Project Geologist for the study of an ancient copper mine at Phu Lon in northeast Thailand in 1985 and 1988. He was also a member of MASCA and provided geological analysis for the studies of crucibles at Ban Chiang and Phu Lon. He retired as Emeritus Professor of Geology and Anthropology from Dickinson College in 1996. William Vernon conducted the study of the Ban Chiang crucibles presented in TAM 2B, chapter 5 and the study of the Phu Lon Complex crucibles reported on in TAM 2C, chapter 2. William Vernon (1925–2018) Vincent C. Pigott holds a Ph.D. in Anthropology (1981) from the University of Pennsylvania, and since 1984 has been the co-director of the Penn Museum’s Thailand Archaeometallurgy Project. He

xiv

is currently a Consulting Scholar in the Museum’s Asian Section. Previously he served as the Museum’s Associate Director and as a Senior Research Scientist in MASCA. After MASCA, he spent a decade as a Visiting Professor at the Institute of Archaeology, University College London. He is focused on the prehistory and archaeometallurgy of mainland Southeast Asia and maintains a strong interest in the origins, transmission, and societal impact of metallurgy across Eurasia. Vincent Pigott’s summary of prehistoric copper production evidence in Thailand and Laos is found in TAM 2C, chapter 2. Vincent C. Pigott [email protected] T. O. Pryce trained in archaeology and archaeological sciences at University College London and Sheffield University, completing his Ph.D. in Southeast Asian archaeometallurgy in 2009. He completed a Leverhulme Trust Early Career Fellowship at the University of Oxford and a Senior Post-Doctoral Fellowship with the Institut de Recherche pour le Développement before being recruited by the Centre National de la Recherche Scientifique (C.N.R.S.) in 2013. Pryce is currently a Researcher at the C.N.R.S, UMR 7528 Prétech and UMR 3685 NIMBE. Oliver Pryce’s lead isotope analyses of the Ban Chiang copper-base assemblage are presented in TAM 2C, chapter 3. T. O. Pryce [email protected]

1 Providing a Regional Socioeconomic Context for Prehistoric Metallurgy in Thailand Joyce C. White technological change results from the decisions and consequent activities of many people­—their contemporaries and their predecessors. (Schiffer 2011:188)

M

etal technologies practiced by prehistoric peoples are inherently social activities. Complex multi-community interactions and specialized knowledge were needed to create products from dispersed natural resources, and to get those products to consumers often located hundreds of kilometers away from the raw materials. As reviewed in TAM 2A, chapter 3, the study of the prehistoric development of metallurgical technologies has moved far beyond Childean perceptions. The narratives now emerging from archaeometallurgical studies acknowledge that there have been many ways past communities have produced and distributed metal products and that consumer bases were diverse. Because the raw materials and specialized knowledge were so widely dispersed, and metal and metal artifact production so often required regional social networks, archaeometallurgy can provide an intimate window into past societies. Since the excavation of copper-base objects at Ban Chiang and other sites in Thailand during the 1960s and 1970s, many metal age sites in Southeast Asia have been explored, and much more is now known about the regional picture for the prehistoric metallurgy of Thailand. Whereas TAM 2B presented in-depth data and analyses from four sites in northern northeast Thailand, Ban Chiang, Ban Tong, Ban

Phak Top, and Don Klang, this volume strives to review and synthesize the excavated archaeometallurgical evidence now available in English from two larger parts of Thailand, the northeast and the central portions. These two regions are drained by the middle Mekong and Chao Phraya Rivers. Metallurgical evidence from these two areas facilitates providing a regional societal framework for the detailed data presented in TAM 2B. Excavations have occurred not only at prehistoric consumer sites like the four in this study, but also, importantly, at several primary production locations. These excavations were conducted by the Thailand Archaeometallurgy Project and other research programs. As this volume will show, a regional picture with great cultural specificity is emerging that illuminates the production of metals, the manufacturing of metal products, the distribution of those products, and the consumption of those products in metal age Thailand. This synthesis should allow Southeast Asia to take its unique place in global archaeometallurgy as the Southeast Asian Metallurgical Province. The metallurgical details, along with other archaeological evidence, also reveal how metal age communities interacted with each other over millennia to maintain peaceful middle-range societies via regional economic networks. To begin the articulation of the prehistoric metallurgical system, Chapter 2 by Vincent Pigott reviews the evidence for primary production of copper from central and northeast Thailand, as well as from central Laos. Both mining and smelting sites

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2C: METAL REMAINS IN REGIONAL CONTEXT

are discussed. Recently available lead isotope analyses for a small sample from two of the four study sites relative to known metal production locations are presented in Chapter 3 by Oliver Pryce. These analyses are beginning to provide the first evidence for specific networks linking metal production localities with consumer groups in prehistoric Thailand. In Chapter 4, the archaeometallurgical evidence that has accrued over the past five decades mainly from consumer societies in the middle Mekong and Chao Phraya Valleys is compiled. Many of these data reside in hard-to-find publications, theses, and manuscripts, yet when pulled together, the data are actually quite extensive. This effort, shouldered primarily by Elizabeth Hamilton, is important as there has been a trend to generalize about ancient metallurgy in Thailand based on selected finds from the most recent excavations. This more comprehensive study puts together quite a different view, a regional picture that demonstrates noteworthy variability in consumer demand. To assist readers with situating the provinces of sites mentioned in these chapters, Fig. 1.1 designates the provinces of Thailand and Laos. Chapter 5 synthesizes the production and consumption evidence to articulate what can now

be said about metal technological systems in prehistoric Thailand. Chapter 6 strives to place the archaeometallurgical evidence from central and northeast Thailand into socioeconomic context for an updated narrative on the social implications of prehistoric metallurgy in this part of the world. The evidence illustrates a regionally distinctive configuration for ancient metallurgy as one of integrative activities that knit together a regional exchange system that endured for hundreds of years, and possibly for two millennia. A critique is also presented of the currently prevalent Higham Model for metal age Thailand. Placing the Ban Chiang metal remains in their larger regional context highlights one of the major contributions of this site to global knowledge of human societies and to understanding relationships between society and technology. Although there may be a two-way street of influence between cultures and technologies, ultimately cultures dominate the choices past societies made in adopting and practicing any technology. The Ban Chiang and Southeast Asian evidence provide an excellent case study against technological determinism; instead, the drivers of technological adoption and change during the metal age in Southeast Asia were local communities.

Figure 1.1 facing  Provinces of Thailand and Laos

2 Prehistoric Copper Mining and Smelting in Southeast Asia: Evidence from Thailand and Laos1 Vincent C. Pigott Introduction

T

here is little at or in archaeological sites that remains static over time. Bioturbation, leaching, organic decay, and erosion are among the various natural agencies at work at sites and on the artifacts contained within over the longue durée. Site formation and degradation processes continue well after human occupation has come to an end. Thus, entropic change is inevitable; nothing remains the same. The discipline of archaeology also exists in a constant state of change, hopefully not entropic, but change just the same. Furthermore, archaeological interpretation is subject to incessant change, i.e., reinterpretation, and nothing in archaeology is more vulnerable to change than chronology. Southeast Asian archaeology as a comparatively nascent Old World discipline has experienced more than its fair share of chronological reinterpretation in recent decades (see TAM 2A, chapters 1 and 3). Significant light has been shed on chronology and its vagaries in the context of prehistoric Thailand and in relation to the site that is the primary focus of this monograph, namely Ban Chiang (see TAM 2A, chapter 2, for a detailed discussion). With this in mind, the discussion now turns to the Khao Wong Prachan Valley (KWPV) in central Thailand, the focus of Thailand Archaeometallurgy Project (TAP) research and of this chapter. The TAP is currently in the midst of a new dating initiative based on accelerator mass-spectrometry (AMS) dates

from domestic seeds (e.g., millet, rice) and charcoal excavated from sites in the KWPV. Until his untimely death in late Spring 2019, Andrew D. Weiss (Consulting Scholar, Penn Museum) was directing the TAP AMS 14C dating program. The author will now assume this role. The TAP samples are being dated at the Oxford University Radiocarbon Accelerator Unit (ORAU) by Drs. Thomas Higham and Katerina Douka. This research is funded by New Zealand’s Marsden Foundation, and is part of a larger, pan-Mainland Southeast Asian dating program directed by Professor Charles Higham (University of Otago, Dunedin) entitled “The Passage of Time. Dating the Prehistory of Southern China and Southeast Asia.” The essential archaeobotanical research behind the TAP dating program has been conducted by a team from Washington State University, namely Professor Steven Weber, Professor Jade d’Alpoim Guedes (now of the University of California, San Diego), and Sydney Hanson. Once the current AMS dating program is complete, close to 100 new seed and charcoal samples from TAP sites will have been dated and the results interpreted. Substantial refinement to the Lopburi regional working chronology is expected (Rispoli et al. 2013:109, fig. 4) with the anticipation that the KWPV site chronology will prove to be earlier than presently understood. However, in this regard it must be noted that any discussion of 14C dating in the KWPV must contend with that portion of the 14C B.P. date to calendar date correction curve

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known as the Hallstatt plateau, where any radiocarbon dates between 2570 and 2350 B.P. all resolve to 800–400 B.C. (Millard 2008) with only a few post-plateau dates present (Andrew D. Weiss, pers. comm. 2019). Both Non Pa Wai and Nil Kham Haeng have dates that fall into this zone, limiting the precision of the corrected dates during this all-important period of site occupation and associated industrial scale copper production in the KWPV. Pending the analysis and publication of the results from the new TAP AMS dating program, the chronology adopted for early copper production at Non Pa Wai is currently based on an earlier series of radiocarbon dates that place this transition in the later 2nd millennium B.C. (see Rispoli et al. 2013), with intensive, large-scale copper production at the KWPV’s enormous smelting sites proceeding well into the 1st millennium B.C. (see below Table 2.2). Furthermore, the upshot of the current interpretation is that Non Pa Wai and Nil Kham Haeng appear to have more temporal overlap than previously anticipated (see below Table 2.2). How and why two such massive smelting sites could evolve at about the same time and in proximity to one another are questions for TAP’s continuing investigations. It must be emphasized that much of the interpretation and discussion concerning prehistoric metallurgical activity and its chronology in the KWPV presented in this chapter should be considered as preliminary in the light of the fact that the final reports for the TAP sites of Non Pa Wai, Nil Kham Haeng, and Non Mak La remain unpublished.

Three Locations with Copper Production Evidence This chapter assesses evidence for early copper mining and smelting activity in two main locations, one in northeast Thailand and the other in central Thailand, and briefly overviews recent evidence from the mining complex at Sepon in Laos. The first location, the Phu Lon Copper Mining Complex (hereafter Phu Lon Complex), is situated along the southern bank of the Mekong River in the northwestern sector of northeast Thailand in Amphoe Sang Khom, Nong Khai Province. Because the Phu Lon Complex

is located so close to the eastern border of the province of Loei where many copper and other ore deposits are known, the site is referred to as situated in the greater Loei region. Here copper mining that dates to the 1st millennium B.C. is associated with ore processing and smelting. The second major early metalworking location is found some 400 km to the south in the KWPV, in Amphoe Kok Samrong and Amphoe Muang, Lopburi Province, located in the Chao Phraya Drainage of central Thailand (see TAM 2A, fig. 6.4). The KWPV has documented evidence of primarily 1st millennium B.C. metallurgy at two massive smelting sites, Non Pa Wai and Nil Kham Haeng, which also yielded evidence of habitation. A third nearby site, Non Mak La, has revealed a habitation/mortuary area and a separate metalworking locus. Also in Lopburi Province, evidence of metallurgy is found in the neighboring Khao Sai On Mineral District (hereafter KSOMD) south of the KWPV. Excavations at the sites of Khok Din and Noen Din have revealed a copper production technological system similar to that employed at Nil Kham Haeng, but on a much smaller scale. Brief mention is made of a third primary copper mining and smelting cluster of sites in central Laos at Sepon. Geologically speaking, the deposit at Sepon is massive, but much of the deeper-lying portions of the orebody remained inaccessible to prehistoric miners. Current research should provide a good sense of just how important these deposits were to the inhabitants of the middle Mekong region in prehistory. Overall, the above-mentioned six sites from Thailand provide the best archaeological evidence known thus far for prehistoric mining and/or metallurgy in the middle Mekong and Chao Phraya Basins and therefore are key to understanding the technological systems employed to produce copper in this region. Copper produced at the sites described here likely supplied many prehistoric settlements in the greater region. As reviewed in TAM 2A, chapter 6, given the alluvial geology of northeast Thailand’s vast Khorat Plateau, viable non-ferrous ore sources are unlikely to be found in any abundance in its Sakon Nakhon Basin where the sites of the Ban Chiang cultural tradition are located. The same is true for northeast Thailand’s Phimai region in the upper Mun Valley, another region well-populated in prehistory.

PREHISTORIC COPPER MINING AND SMELTING

Within Thailand, the lack of ore sources in these regions removes a substantial portion of the country from the realm of possible ore-providing zones and necessitates that evidence for ore sources be sought elsewhere. At the same time, at sites across northeast Thailand, evidence not only for finished products, but also for metalworking (e.g., casting of copper-base metal products) is archaeologically well documented (see TAM 2B, chapter 5, and Chapters 4 and 5, this volume). Thus, the metal found at the prehistoric mortuary/occupation sites in the Sakon Nakhon and upper Mun Basins must have been imported from other localities. The Phu Lon Complex does have evidence for tin bronze alloying. In the KWPV, at Nil Kham Haeng, tin bronze is also evidenced in a very small number of artifacts from burials. Slag analyses from the site also show traces of tin perhaps reflective of recycling of metal (Pryce et al. 2010:255) or, perhaps of tin bronze production itself. Moreover, the possibility that tin bronze artifacts arrived via trade and exchange cannot be ruled out. The scale of mining evidence and accumulated production debris as well as the paucity of metal artifacts at the sites discussed herein suggest that some form of finished product, most likely the intermediary product of copper-base metal ingots, was being exported to other regions. Copper ingots, for example, could have been transported from any of these production sites to villages in the Sakon Nakhon Basin and elsewhere in Thailand as well as the larger region to be cast into implements, jewelry, and other finished products, often after having been alloyed with tin. Excavations at Sakon Nakhon Basin settlements have yielded numerous finished copper-base products, along with evidence suggestive that local metalworkers produced copper alloys, including tin bronze, and, in turn, manufactured such metal products from these alloys. In fact, a strong argument has been made that copper from central Thailand (i.e., the KWPV), and perhaps later artifacts or ingots in tin bronze, were moving to sites in the Phimai region during phase BA2 (1000–900 B.C.) at Ban Non Wat (Pryce 2012a; Pryce et al. 2011a:3320; see map in Higham and Rispoli [2014:3, fig. 1]; see also discussion below). Thus, final manufacturing steps may well have occurred in proximity to consumers, and, as a result, finished products were adapted to local needs and

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tastes. Some evidence is also discussed that links ore-processing behaviors in Loei to those in Lopburi Province.

Ore Sources and Early Mining Exploitation As described in TAM 2A, chapter 6, understanding the prehistoric metallurgical industry in the region begins with the study of the geology of the region’s metallogenic zones (see TAM 2A, figs. 6.4 and 6.5). In northeast Thailand, the Khorat Plateau that makes up much of the region is a vast expanse of alluvium divided by the Phu Phan Hills into two shallow basins, the Khorat and the Sakon Nakhon (see TAM 2A, fig. 6.2); the two basins lack deposits of non-ferrous base metals such as copper, lead, and zinc. Before and after the excavations at Ban Chiang in the 1970s, teams of Thai and international geologists conducted numerous extensive surveys in northeast Thailand (e.g., Jacobson et al. 1969). The best-known ore-rich region near the Khorat Plateau is in Loei Province, which abuts the Plateau along much of its long western escarpment. Decades of economic geological surveys in the region, some conducted by Udom Theetiparivatra of the Thai Department of Mineral Resources, show how rich and diverse the ore deposits of Loei Province are (Javanaphet 1969: fig. 5.6). Evidence of pre-modern mining activity at the Phu Lon Complex was identified during these early Thai geological surveys. At the second mineral-rich location well to the south in the KWPV on the alluvial Lopburi Plain in central Thailand, economic geological surveys have been few. While the inselbergs that edge this valley have copper deposits, the greater region is devoid of such resources. Nonetheless, the KWPV’s inselbergs do show evidence of pre-modern, presumably ancient mining (Natapintu 1988:115, table 2; for a brief overview of the environment of the KWPV see Higham and Rispoli [2014:4]). Despite decades of archaeological work in Thailand, few projects have focused on identifying primary copper production sites, and, so far, no other known ore deposits with evidence of prehistoric mining have been identified in the country other than those at the Phu Lon Complex and in the Lopburi

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2C: METAL REMAINS IN REGIONAL CONTEXT

region. Evidence of pre-modern/ancient mining from elsewhere in Southeast Asia remains sparse, with the exception now of Sepon in Laos where investigations have identified prehistoric copper shaft mining across the surface of a major orebody. This mining activity has been dated to the early 1st millennium B.C. (MMG LXML Sepon 2016; Pryce et al. 2011a:3310; Sayavongkhamdy et al. 2009; Tucci et al. 2014). Beyond the Thai and Laotian evidence, at present, one has to look outside Southeast Asia to the north into the People’s Republic of China (hereafter PRC) for additional evidence of substantial ancient copper mining (e.g., Shizong et al. 1993; Vogel 1982; Wagner 1986). Investigation of other metalore-rich regions of Southeast Asia is essential for an improved understanding of prehistoric metallurgical developments across the greater region. Current data on the Phu Lon Complex resulted from survey and excavations by TAP (e.g., Natapintu 1988; Pigott 1988, 1998; Pigott and Natapintu 1988, 1996–97; Pigott and Weisgerber 1998; Pigott et al. 1992; Pryce 2012a; Pryce et al. 2011a, 2011b, 2014; Vernon 1996–97; White and Pigott 1996). The evidence from central Thai sites is the result of archaeological fieldwork and subsequent research conducted first by Surapol Natapintu (then of the Fine Arts Department) and the Central Thailand Archaeological Project (e.g., Natapintu 1984a, 1984b), followed shortly thereafter by both the TAP and the Thai-Italian Lopburi Regional Archaeological Project (LoRAP). In central Thailand, TAP has focused on documenting ore sources exploited and high temperature processes used at prehistoric copper smelting sites that were, to varying degrees, both habitation and production sites (e.g., Higham and Rispoli 2014; Natapintu 1987, 1988, 1991; Pigott 1999; Pigott and Natapintu 1988, 1996–97; Pigott et al. 1997, 2006; Pryce 2009, 2012a, 2012b; Pryce and Pigott 2008; Pryce et al. 2010, 2011a, 2011b, 2014; Rispoli et al. 2013; Weiss 1989; White and Pigott 1996). LoRAP focused on the satellite industrial locus of the KSOMD, south of the KWPV, where small-scale copper production exploited nearby pockets of copper ores also during prehistory (Ciarla 2007b, 2008; Higham and Rispoli 2014; Pryce et al. 2013; Rispoli et al. 2013). The data from the TAP and LoRAP research programs provide the bulk of the empirical evidence presented in this chapter.

Northeast Thailand: The Greater Loei Region The Phu Lon Complex: Mining and Smelting For purposes of discussion, the following terms, as defined herein, are used to refer to the Phu Lon Mining Complex as well as to distinct activity areas on the grounds of the Complex: •

hu Lon Complex: the entire area of prehistoric P and later mining and smelting activity located on and surrounding two hills (I and II) containing copper orebodies on the south bank of the Mekong River at 18°204 N, 102°140 E (see Pryce and Abrams 2010).

•

Phu Lon I: (For location see Figs. 2.1 and 2.2.) The hill/orebody situated immediately south of the Mekong River. This is the location of the majority of the mining evidence visible on the surface. Various mining locations named but not individually discussed can be found on Figure 2.2.

•

hu Lon II: (For location see Fig. 2.1.) This hill/ P orebody is located immediately to the south of Phu Lon I, separated from it by a narrow valley between the two hills. Modest mining rubble deposits were apparent on Phu Lon II along with a large ore-crushing anvil (see Fig. 2.12), suggesting that processing of mined ore took place here as well.

The TAP site survey in Loei Province in 1984 included one week of test trench excavation at the locus known as the Pottery Flat at Phu Lon I, undertaken by Surapol Natapintu, Udom Theethiparivatra, and the author, with the assistance of a team from the Northeast Thailand Archaeological Project (NETAP) based in Khon Kaen and of local workers (Pigott 1984). This was followed by a three-month excavation season in 1985 (Pigott 1985). This fieldwork demonstrated that over the centuries numerous prospecting pits, adits, shafts, and galleries had been opened at the Phu Lon Complex, evidencing extensive mining activity dating primarily to the 1st millennium B.C. (see Fig. 2.3 and Table 2.1). These

PREHISTORIC COPPER MINING AND SMELTING

Figure 2.1  Schematic diagram of the location of the hills/orebodies of Phu Lon I and II. Adapted from Kamvong and Zaw (2009:626).

9

10

2C: METAL REMAINS IN REGIONAL CONTEXT

Figure 2.2  Contour map of the mining locations of Phu Lon I. Adapted from Pigott and Weisgerber (1998:138, fig. 5).

PREHISTORIC COPPER MINING AND SMELTING

mining activities were concentrated on the two adjacent large copper-containing hills of Phu Lon I and Phu Lon II. Phu Lon I is the location of the primary mining locus and nearby is the associated ore-processing activity area called the “Pottery Flat.” Phu Lon II is another ore-rich hill just to the south where some mining activity also took place, but not on the scale apparent at Phu Lon I. On the hill of Phu Lon I, centuries of mining resulted in an orebody honeycombed with shafts and galleries that at an unknown point in time resulted in the collapse of the hill. The scale of the mining combined with the vast quantities of tailings significantly altered the topography of the hill and reduced its vegetation cover (Color Fig. 2.4). The Thai name Phu Lon means “Bald Mountain,” and the present-day hills (Phu Lon I and II), when compared to the surrounding hillsides, are still relatively sparsely vegetated, with low-lying weeds and scrub bushes on the grounds of the mine and tailing piles. This sparser vegetation sits in striking contrast to the oak-dipterocarp/bamboo forest of the surrounding hills. Phu Lon I has several activity areas identified nearby for mining and ore processing, including Udom’s Rock, Bunker Hill, the Pottery Flat, and Ban Noi (Fig. 2.2). While the ore-rich hills of the Complex are briefly described below, the discussion to follow centers primarily on locations at and activities conducted therein on Phu Lon I. The basic geology of the Phu Lon Complex has been well

Figure 2.3  Phu Lon Mining Complex 14C dates.

11

documented over the years. Udom Theetiparivatra and his Thai Department of Mineral Resources colleagues (e.g., Yamniyom et al. 1973) conducted several surveys of the Complex prior to 1985. In 1985, TAP geologist William W. Vernon resurveyed the entire Complex, but his survey remains unpublished. More recently, additional papers have been published on the economic geology of the Phu Lon Complex (e.g., Kamvong and Zaw 2005, 2009; Kamvong et al. 2006). Some 250 million years ago the Triassic period collision of two pieces of continental plate, namely the Sibumasu (Shan-Thai) and Indochina Terranes (see TAM 2A, fig. 6.3) resulted in significant metallogeny, i.e., the emplacement of the orebodies that dot the landscape along the zone of contact running from northeastern through central Thailand (Buffetaut and Ingavat 1985:80–81; Bunopas and Vella 1992; Pigott and Weisgerber 1998:136, fig. 2). As a result of his field survey, Vernon has indicated that the heavily weathered copper orebodies that comprise Phu Lon I and II consist of typical contact metasomatic deposits composed of sulfide orebodies with an indigenous oxide zone (gossan) exposed at the surface (Pigott and Weisgerber 1998:136, fig. 3; also Rostoker et al. 1989:71, fig. 2; and see Figure 2.5 in this volume). In these orebodies, the upper deposit weathered over time in Loei’s heavy monsoon rains, and the result was a rich concentration of

charcoal

P-3457

charcoal

charcoal

charcoal

charcoal

B-17051 2580±80 NA

B-17053 3290±70 NA

B-17057 2580±70 NA

B-17058 2690±80 NA

TAP 85 S#-9

TAP 85 S#-19

TAP 84 S#-4A, S#-4B, & S#-5

TAP 85 S#-142

TAP 85 S#-143

Ban Noi, Test Trench 1, Area B, Stratum 3a

Udom’s Rock, 1.41 m below datum in Trench UR5

TAP 85 S#-170

TAP 85 S#-150

Pottery Flat, TAP 85 S#-165 Baulk between A3 and A4, beneath Stratum 1 in Area 1

Pottery Flat, Square A1, Stratum 1, Area 5

Pottery Flat, Square A1, Stratum 1, Area 15

Pottery Flat, Trench 1 and 3, Stratum 1

Bunker Hill, Long Trench 3

Bunker Hill, B10

Provenience

Phu Lon Sample No.

Note: b.p. = before present; NA = not applicable; NaOH = sodium hydroxide; m = meter. *As determined by Beta Analytic Testing Services, Miami, FL., USA.

charcoal mixed with soil

B-17052 2420±90 NA

2360±60 -26.34

charcoal

Sample

B-17054 2140±70 NA

C/ C 12

charcoal mixed with soil

13

B-17055 1150±90 NA

Lab No.

14C Age b.p.

acid/alkali/acid

acid/alkali/acid

acid/alkali/acid

acid/alkali/acid

acid/alkali/acid

no NaOH

acid/alkali/acid

acid/alkali/acid

Pretreatment

382–2 B.C.

A.D. 675– 1024

Calibration

charcoal collected from screening of matrix of Stratum 3a

small concentration of charcoal in layer of mining rubble

charcoal concentration

charcoal collected from screening of matrix of a locus within 1 x 1 m square

charcoal collected from screening of matrix of a locus within 1 x 1 m square

1054–569 B.C.

897–419 B.C.

1739–1431 B.C.

898–417 B.C.

794–373 B.C.

combined charcoal sample 753–234 B.C. from Stratum 1, in 2 trenches

small concentration of charcoal in red clay layer

soil extracted from red soil stratum from section of Bunker #10, screened and charcoal collected

Excavation Context

Table 2.1  Radiocarbon Determinations* from the Phu Lon Complex (calibrated with OxCal 4.1, Reimer et al. [2009] data)

12 2C: METAL REMAINS IN REGIONAL CONTEXT

PREHISTORIC COPPER MINING AND SMELTING

13

Figure 2.5  Schematic diagram of the weathered copper sulfide orebody at Phu Lon I. (Diagram by William W. Vernon.)

the copper carbonate ore malachite, Cu2CO3(OH)2, that was readily accessible to ancient miners through open-pitting and shaft mining. The malachite was also deposited in fractures in the friable skarn matrix of the orebodies, often in association with cavernous quartz veins. These large quartz veins are close to the surface and are found throughout the entire mining area (William W. Vernon, pers. comm.). Prior to mining activity, the exposed gossan cap, where not covered by vegetation, would have been distinctively multicolored, with the earthy red of iron oxides and the green stains of oxidized copper ore serving as a beacon of sorts, indicating the presence

of ores and minerals such as malachite, gem-quality rock crystal, and iron ocher, useful as a pigment and as a grave good in prehistory. Peoples moving on foot or by watercraft along the Mekong through this relatively rugged mountainous area could have spotted the Phu Lon Complex’s mineral riches due to its colorful outcrops. Prehistoric peoples may have been drawn to ore deposits in the first place because of a desire for decorative minerals such as red ocher. The multihued, weathered gossan cap of such orebodies not only would have been topographically pronounced due to its natural erosion resistance, but also mining would denude it of vegetation.

14

2C: METAL REMAINS IN REGIONAL CONTEXT

Prior to mining, closer surface inspection would have revealed the deposits of green malachite embedded in the margins of the quartz veins or in seams shot through the skarn host rock. Both of these relatively friable matrices facilitated mining using stone mauls, often igneous river cobbles collected locally from the bank of the Mekong River. The size and weight of the mauls found at the site range from ca. 1–4 kg (see Fig. 2.6). A few of the cobble mauls are grooved or notched for hafting, but most have smooth surfaces. There are methods of hafting, however, that would not have left traces on the stone mauls themselves. An example would be the unique Central Asian tin mine discovery of a wooden maul handle carved in such a way as to provide a flat platform at the top to which the maul was then lashed without need for chipping or grinding hafting grooves in the maul itself (Stöllner et al. 2011:242, fig. 10). Hafting a maul onto a handle would have made for a much more effective mining tool. Swinging the mauls against the host rock, the miners would have followed the veins of brittle quartz, breaking the rock as they went in order to obtain the malachite trapped within. The topography, mining, and ore-processing locations of Phu Lon I are presented in Figure 2.2 (Pigott and Weisgerber 1998:138, fig. 5). Prehistoric shafts are apparent in the cliff called the West Face and in Peacock Cave (itself a large gallery) and its associated flat, composed of the Peacock Flat and South End. The Pinnacle (Color Fig. 2.7) and Udom’s Rock (Color Fig. 2.8) are enormous formations of host rock riddled with shallow surface pits or adits and, at times, shafts that followed copper veins and sought ore pockets (Fig. 2.9; see also Natapintu 1988:111, figs. 2, 3). The West Face and the Pinnacle offer an indication of the minimum height of the hill of Phu Lon I prior to prehistoric mining activity, while the location of Udom’s Rock marks the probable western flank of the hill itself. Excavation of the Pottery Flat revealed that it was an ore crushing and smelting locus comprised of a ca. 50-cm-thick layer of crushed ore and slag(?), while Bunker Hill was rich in large fragments of quartz broken out of ore-rich veins; both loci yielded abundant cordmarked potsherds and broken crucible sherds. The large central depression at the base of the sheer cliff of the West Face is termed the Lower Flat. The presence and configuration of this depression signal that

the entire original west side of the hill of Phu Lon I was mined for an extended period. The argument has been made that this large depression was created by the collapse of the area under the enormous weight of accumulated mining debris above it (Pigott and Weisgerber 1998:140); the hill of Phu Lon I had become so riddled with underground shafts and galleries that eventually the entire mining area collapsed, a not uncommon occurrence in mining history worldwide.

Mining Activity Areas udom’s rock The earliest mining activity at Phu Lon I appears to have taken place on Udom’s Rock, where relatively shallow pits with rounded configurations and smooth, rounded interiors can still be seen (e.g., Pigott and Weisgerber 1998:141–143, figs. 5, 9–11; also see Color Fig. 2.8). Such configurations are characteristic of the use of hand-held stone mining mauls to crush the rather friable host rock matrix in order to get at the malachite-bearing quartz veins that riddled the hill of Phu Lon I. No evidence was noted here or anywhere at the Phu Lon Complex of the use of fire-setting to weaken the host rock before mining (e.g., no concentrations of charcoal in shafts and/or galleries or in tailings outside shafts). Prehistoric miners at Phu Lon I were extracting copper ores in order to smelt copper metal, and this metal was being alloyed with tin to make bronze on the site (see below). The casting of durable tin bronze mining picks might have been within the capabilities of the available local technological system during the 1st millennium B.C.; however, no shafthole pick or mattock—known elsewhere in Eurasia—has yet been identified anywhere in Southeast Asia for the prehistoric period. Evidence for the use of metal mining tools at Phu Lon I relates to later mining activity (of uncertain date) in shafts that had originally been worked with stone mauls.

the pinnacle This tall, freestanding remnant of host rock sits on the Lower Flat at Phu Lon I (see Color Fig. 2.7). Vestiges of shafts are visible higher up on the face of the Pinnacle as well as along its base, where shaft clearing was undertaken during the TAP 1985

PREHISTORIC COPPER MINING AND SMELTING

15

season (see Pigott and Weisgerber 1998:143– 146, figs. 5, 12–15, and 17). Metal mining implements may have come into use to mine such shafts only with the advent of iron production later in the 1st millennium B.C. A forged-socket iron-mining implement (e.g., a chisel or a pick) of unknown date was found on the surface at the base of the Pinnacle where secondary shafts are present. These shafts were dug after the collapse of the hill of Phu Lon I due to over-mining. Some of these basal shafts bore evidence of possible metal tool marks. However, the majority of mined locations at the Phu Lon Complex indicate that prehistoric miners used minimally worked stone mauls with great success. Figure 2.6  Stone mining maul made from a local igneous river From the fill in two of the Pinnacle basal cobble. The extent of spalling and pecking (at both ends) suggests this maul may have been discarded when exhausted. It was one of mine shafts came two amorphous lumps of hundreds of hand-held mining and ore-crushing stone implements copper-base metal. These lumps were precollected from the surface at Phu Lon I by geologist Udom Theetisumably casting spillage that washed into the parivatra (Dept. of Mineral Resources). mine shafts as they filled with soil gradually over time. PIXE analysis undertaken through MASCA demonstrated one sample to be a lump of tin bronze (6.91% Sn) with trace amounts of lead, left “as-cast” (Pigott 1988:37, table 1, fig. 2). The Phu Lon copper deposit is known to contain appreciable lead as an impurity; with lead present at trace element levels in the lump, it is possible that this sample came from smelted Phu Lon copper alloyed with tin. However, no lead isotope analysis (hereafter LIA) of the lump has confirmed a source from Phu Lon copper. A single LIA test by T. O. Pryce’s Southeast Asian Lead Isotope Analysis Project (hereafter SEALIP) of the second amorphous lump of bronze (SEALIP/TH/PL/9), also from one of the Pinnacle mine shafts, indicated that the sample has a signature compatible with that of the Phu Lon production field (Pryce et al. 2011a:3315). In the process of clearing the fill from a mine shaft at the base of the Pinnacle, a single ceramic pedestal vessel (“dish-on-stand”) was encountered on or near a small ledge in the shaft itself. This Figure 2.9  Sinuous mine shaft sunk in the base of the Pinnacle at Phu Lon I. This shaft must postdate the implosion of the hill of Phu Lon I. Given the smooth configuration of the shaft walls it appears to have been mined with stone mining mauls, which in turn suggests a possible prehistoric date for its mining. (Scale: white color bar = 50 cm.)

16

2C: METAL REMAINS IN REGIONAL CONTEXT

artifact bore a red slip and was described as a typical 1st millennium B.C. shape (Natapintu 1988:112, fig. 5). The possibility exists that the vessel could have been placed in the shaft purposefully, perhaps to hold an offering or to act as an oil lamp.

bunker hill This locus at Phu Lon I lies ca. 150  m to the northeast of the main mining area, the latter comprised of two other loci, the Peacock and Lower Flats (see Fig. 2.2). The name Bunker Hill derives from a cluster of 20th century Thai Army bunkers dug into the archaeological deposit on a small hill that overlooks the Mekong to the north. Excavation here was often one of salvaging vestiges of intact stratigraphy preserved in bunker sidewalls or between bunkers. In prehistory at Bunker Hill, malachite-rich, cavernous quartz veins ca. 1 m below current ground level were being exploited. Once a major quartz vein was located, the miners proceeded to smash the quartz (often in large crystal form) from the vein in order to extract adhering malachite. Quantities of smashed and crushed quartz characterized the stratigraphy of Bunker Hill. Intermixed in this debris were four crucible sherds, whose presence suggests copper/bronze processing activity at this locus. These four examples resemble the crucible sherds found at the Pottery Flat, although the number is too small to draw any useful conclusions. Numerous heavily worn, small, cordmarked potsherds and stone tools for mining and crushing were also excavated at Bunker Hill. Ceramic analysis by Vernon, although made difficult by the poor condition of the potsherds, indicated a basic similarity in terms of fabric and cordmarking with potsherds found on the nearby Pottery Flat some 50  m south and slightly uphill. Bunker Hill 14C dates demonstrate activity contemporaneous with that of the Pottery Flat, ca. 1st millennium B.C. A later date also documents that some activity occurred at this locus well into the protohistoric period, ca. 4th to 10th centuries A.D. (see Fig. 2.3 and Table 2.1).

Ore Processing the pottery flat

In the study of ancient mining in the Old World, it is not uncommon to document a prehistoric

mining site where, in the immediate vicinity of the mine, copper ores were being crushed to fine, often pea-sized fragments (e.g., O’Brien 1994). At Phu Lon I, the ore-processing activity area known as the “Pottery Flat” was first test excavated in 1984 during the TAP site survey and then extensively excavated during the 1985 season. The Pottery Flat, about 50 m north of Bunker Hill, is 150 m north and east of the main mining area at Phu Lon I (see Fig. 2.2). The prehistoric processing of ore on the Pottery Flat involved two distinct, sequential activities. The first was the hand crushing of the larger fragments of mined ore into small, pea-sized gravel fragments. This act of crushing then facilitated the second activity, beneficiation, the separating by hand of the rich green malachite ore from the friable and finely crushed host rock and/or from the quartz vein matrix in which the ore also could be embedded (O’Brien 1994:173). It is important to note that the crushed ore and slag deposit on the Pottery Flat is identical in texture to the massive, meters-deep deposit that comprises the ca. 5-hectare site of Nil Kham Haeng (discussed below) in the KWPV, some 400 km to the south. The ore fragments resulting from crushing were of a relatively uniform size, with fragments ca. 0.5 cm on average (Fig. 2.10a, b), and these were deposited in a single stratum that in its main concentration ranged in thickness from 15–50 cm; the stratum was spread over an area of at least 200 m2. On the stratum’s surface and within its matrix, hundreds of intact and fragmentary hammerstones and stone anvils for ore crushing were found (Fig. 2.11; see also Natapintu 1988:112, fig. 4, 117, fig. 6). The prevalence, distribution, depth (ca. 50 cm), and expanse of the crushed gravel deposit signal that ore crushing was the primary activity on the Pottery Flat and that it was done on a substantial scale over time. The Pottery Flat could have been chosen for ore processing not simply because it was close to the mining area, but also because it is relatively horizontal and near to vegetation that would provide miners shelter and fuel while they were living at the site, most probably during the dry season. It has been suggested that mining expeditions from villages in the greater region may have been dispatched to the Phu Lon Complex during this period in order to obtain copper and to make bronze (Pigott 1998; White and Pigott 1996). There is, however, no evidence of

PREHISTORIC COPPER MINING AND SMELTING

Figure 2.10a  Profile view of excavations on the Pottery Flat on Phu Lon I showing (in the baulk) the single stratum of crushed copper ore, host rock, and perhaps slag that extended across the ca. 200 m2 of this ore-processing locus. Surapol Natapintu, who directed excavations here, is seen in the background.

17

Figure 2.10b  Close-up of the Pottery Flat stratum of crushed material from Phu Lon I. (Scale in centimeters.)

permanent habitation found anywhere at the Phu Lon Complex. On the Pottery Flat, the amount of metalworking debris and its uniformity suggest that ore crushing was a group activity. It is likely that the individuals doing this work included some of the miners who had transported the ore over to the Pottery Flat. It is also possible that women and children, who could have traveled with the mining party, assisted in the Pottery Flat activities. Hammerstones and anvils were rather randomly distributed across the entire breadth of the ore-processing activity area, with what appear to be occasional clusters of such implements that constitute crushing stations. The hammerstones were of various shapes and sizes, but generally smaller than the large, heavy cobble mauls known from the mining area proper, and could easily fit in the palm of the hand. Hammerstones typically have distinct zones of pecking on their ends and edges. Flat-surfaced anvil stones that provided the surface against which the ore would have been crushed, come in all shapes and sizes. At Phu Lon II, a single large anvil stone with a series of ore-crushing depressions lining its entire outer edge (Color Fig. 2.12) was found on the surface after having been exposed in a road cut. This Figure 2.11  View looking south across the Pottery Flat, showing the excavated surface of the single stratum of crushed material from Phu Lon I that extended across the ca. 200 m2 of this ore-processing locus. Most of the stones seen on the surface are either hammerstones for ore crushing or anvils against which the ore was crushed. (Scale: white color bar = 50 cm.)

18

2C: METAL REMAINS IN REGIONAL CONTEXT

stone anvil is sufficiently large to have accommodated a small group seated around it, each using an individual crushing depression along its outer rim. Such depressions form over time from the repetitive act of crushing ore in the same location on the anvil. Additional evidence of ore processing came from Phu Lon II in the form of a surface find of a piece of slag. Lead isotope analysis of this sample (SEALIP/ TH/PL8), which had a copper content of 1–2 wt% (weight percent), suggests it was a product of a “relatively efficient” smelting process using Phu Lon copper ore (Pryce et al. 2011a:3315, 3316). The advantage of beneficiating the ore near the mine was that removing the gangue, or unwanted siliceous impurities bound to the ore, greatly reduced the volume and mass of the ore. Beneficiation, in turn, meant that rich ore with less gangue was charged into the smelting crucibles. If the ore was destined to be smelted elsewhere, beneficiation to extract the richest ore bits would lighten considerably the burden of transportation. Slag was not a common or obvious find on the Pottery Flat, with only a few larger fragments found (see Pryce et al. [2011a:3315–3318] for the analysis of one sample). The process of smelting can produce slag in some quantity, far more than the small amounts of slag found adhering to the crucible sherds. The paucity of slag at this locus can be explained in various ways. Some portion of the beneficiated ore might have been transported elsewhere for smelting, or it is possible that the large quantity of finely crushed ore and host rock that made up the single stratum here also contained slag crushed to extract prills of copper that were remelted, or perhaps the slag was directly resmelted for its residual copper. At the time of excavation, the possibility that slag was being finely crushed as well as the host rock had not been considered and the crushed debris on the Pottery Flat and at Ban Noi was not closely examined for slag. Another explanation for the relative absence of slag on the Pottery Flat is that poor reducing conditions can produce unrefined copper trapped in slag that may also contain partially reduced ore fragments. Such an unrefined mass could have been shipped to consumer locations where it was refined (see Craddock 1995:202). A low incidence of slag might also result if hand-sorted, low gangue, copper-rich malachite

ore fragments were being charged. Smelting such rich ores results in minimal slag (Pigott and Weisgerber 1998:153–155; Tylecote 1974). These rich ores would have been easily accessible in the upper reaches of the Phu Lon Complex’s orebodies. A few fragments of malachite were excavated on the Pottery Flat. The evidence from Phu Lon I mining and ore processing strongly suggests oxidic ores like malachite were being exploited. There is no indication that the deeper-lying copper sulfide ores of the Phu Lon Complex were exploited or that the process of co-smelting of sulfide and oxide ores occurred at Phu Lon I. The latter process would generate a greater amount of slag if practiced (Rostoker et al. 1989).

ban noi The locus known as Ban Noi lies 50  m downhill towards the Mekong River to the north of the hill of Phu Lon I. It is a low, mounded activity area about 5 m in diameter and 1 m deep. Its matrix was composed of thin lenses of finely crushed ore very similar to the deposit excavated on the Pottery Flat as well as to the massive (ca. 5 hectares) deposit that comprises the site of Nil Kham Haeng in the KWPV of central Thailand. Thus, Ban Noi is quite similar to but much smaller in total size than the Pottery Flat. Ores (and perhaps slag) were finely crushed here and the rich ore bits (and perhaps copper prills) were picked out by hand. A single 14C date from charcoal (B-17058) in the site’s gravel matrix dates the lower levels of the Ban Noi deposit to the first half of the 1st millennium B.C., making it contemporaneous with similar activity on the Pottery Flat (see Table 2.1). The ceramics, small cordmarked potsherds from the lower levels, resemble those from the Pottery Flat as well. From the uppermost portion of the deposit, sherds with appliqué were found along with ceramic net sinkers. A single tin bronze socketed adze/axe was found at the base of the Ban Noi deposit (Natapintu 1988:117, fig. 7). This artifact was analyzed initially under the author’s auspices by PIXE through MASCA, indicating it was a tin bronze with ca. 10% tin content. Most recently it was reanalyzed by SEALIP, which confirmed that the artifact was produced from local copper, and also confirmed that the sample (SEALIP/TH/ PL/10) had a ca. 10.3 wt% tin content (Pryce et al. 2014:285).

PREHISTORIC COPPER MINING AND SMELTING

Smelting, Melting, and Casting the pottery flat Although ore crushing and sorting for rich ore bits were often performed at mining sites in prehistory (e.g., Merkel 1985; O’Brien 1994), evidence for ore smelting at such sites is less common. The Pottery Flat at Phu Lon I contained a single stratum of uniformly sized, crushed ore and host rock fragments and yielded evidence of pyrotechnological activity in the form of crucible and bivalve mold fragments. This evidence strongly suggests that in addition to ore preparation, at least some copper ore was smelted in the crucibles here. A second form of pyrotechnological activity on the Pottery Flat may be represented by the occurrence of cordmarked sherds of locally made pottery. In addition, other production activities took place here, as there is evidence for the manufacture of chipped and groundstone adze/axes (e.g., flakes, broken adze/axes) as well as of stone bracelets (e.g., blanks, broken bracelets). Most of the crucible sherds from the Pottery Flat come from crucibles very similar in shape to those recovered from Ban Chiang (TAM 2B, chapter 5) and other Sakon Nakhon Basin sites, as well as sites in the upper Mun Phimai region (e.g., Ban Non Wat, Higham and Kijngam [2012a: fig. 18:4]) and in central Thailand (e.g., Noen Klong Bamrung, Natapintu [1988:121, 122, fig. 14a]). This crucible type has been termed the “common Southeast Asian crucible type” (White and Hamilton 2009:365); these crucibles may be present at Sepon in Laos. Evidence from both Ban Chiang (TAM 2B, chapter 5; see also Vernon 1997; White et al. 1991) and Phu Lon’s Pottery Flat suggests that there were two types of crucibles in use based on rim morphology: one type that tapers to a thin rim edge and a second type with “a relatively uniform thickness with a rounded edge” (Vernon 1996–97:810–811, table 1, 819, plate 2). Six examples of the rounded rim type contrast with some 25 of the tapered rim type out of the 96 crucible sherds examined in Vernon’s initial Phu Lon study (Vernon 1996–97:811). Whether the rounded rims came from a body type different from the spouted crucible examples could not be determined due to the small size of the crucible sherds. Interestingly, another Thai site, Ban Non Wat in southern northeast Thailand, also yielded evidence of the two rim types. See Cawte (2012:458–462) for

19

an extended crucible discussion with speculations on their use at Ban Non Wat. The Phu Lon crucibles are, however, of a rather small size for a vessel designed to contain a smelting reaction involving crushed ore and pieces of charcoal. Vernon (1996–97:811) estimated that on average the diameter of the bowl portion of a typical crucible was about 60–75 mm with a depth of 30–35 mm. With the spout included he suggested an effective capacity of ca. 35–65 cc. In addition, their presence at the above sites where there is little direct evidence for smelting lends credence to the argument that such vessels were used primarily for melting and pouring molten metal. However, Vernon (1996–97:815) did infer from an analysis conducted by M. R. Notis and H. Moyer at Lehigh University of slag recovered from the interior of a Pottery Flat crucible sherd that smelting was occurring in some of these crucibles. Were the small spouted crucibles used for smelting despite their diminutive size? If so, the amount of metal produced during each smelt would have been remarkably small (compare the fluid metal capacities of crucibles discussed in TAM 2B, chapter 5). Vernon studied a total of 114 crucible sherds excavated from the Pottery Flat (Vernon 1996–97; see also Vernon 1997; White et al. 1991). Most of the fragments were body sherds of crucibles, while some were of pouring spouts. That these crucibles may actually have been used for smelting is suggested by the occurrence of occasional crucible sherds that are heavily slagged, with, at times, indications they were reused. The slagged crucibles can contain prills of copper and prills of copper and tin together. Where the latter prills occur together they offer strong evidence of the practice of on-site alloying to produce tin bronze (Vernon 1996–97). It is not clear in what form the tin occurred and from where it may have come. One suspects that it traveled to the Pottery Flat in ingot form as there is no direct evidence for the smelting of tin at this locus. No amorphous fragments of casting spillage were identified during excavation on the Pottery Flat. The Pottery Flat crucible evidence, when combined with the presence of two bivalve mold fragments, one in sandstone with an X incised in its exterior surface (Fig. 2.13), and another in ceramic, suggests that socketed implements were being cast from locally smelted ores on the Pottery Flat. Further supporting evidence for smelting at the Phu Lon

20

2C: METAL REMAINS IN REGIONAL CONTEXT

Complex comes from LIA performed by SEALIP. Though initially it was reported that LIA had suggested that the socketed adze/axe excavated at Phu Lon I’s Ban Noi locus (see below) was not made from local copper ores (Pryce 2012a:116, 119; Pryce et al. 2011a:3315), this report has been revised and LIA does suggest its signature is roughly compatible with that of the Phu Lon copper deposit (Pryce 2013:2783). However, it must be stated that the Phu Lon production signature itself is highly dispersed (Pryce 2012a:116, 119; Pryce et al. 2011a:3315). All in all, the above evidence combines to indicate that mining, ore crushing, and beneficiation followed by smelting, alloying, melting, and casting were all being performed at Phu Lon I. While petrographic analysis of crucible sherds from Phu Lon I was conducted by Vernon (1996–97), a more detailed analysis of the slagged crucible interiors in order to shed additional light on the smelting process would prove useful (see Pryce et al. 2011a:3315–3318; Wayman et al. [1988] discuss methods of tin bronze manufacture in antiquity; see also Pigott and Weisgerber 1998:159, note 3; Pigott et al. 2003; see TAM 2A, chapter 6, for discussion of tin and its potential sources in the region).

ban noi At Ban Noi twelve crucible sherds and minor amounts of slag were found. Small, circular depressions in the crushed gravel could represent locations where crucibles were being heated. Charcoal was disseminated throughout the deposit. The single socketed tin bronze adze/axe from Phu Lon I was excavated here at the interface of the gravel deposit and sterile soil (Natapintu 1988:117, fig. 7). Though the suggestion is pure speculation, one wonders if it might have been placed there deliberately at the start of production activities at this locus. A single tin bronze adze/axe, as mentioned above, was made from Phu Lon copper ore. This artifact is well dated by 14C to the first half of the 1st millennium B.C. (see Fig. 2.3 and Table 2.1). No fragments of casting spillage were identified during excavations at Ban Noi. The Phu Lon bronze adze/axe has similarities in both size and shape with an example excavated in Ban Chiang BC Burial 23 from the upper Early Period Phase Va (BC 694/1203A, TAM 2B, fig. 3.10a; White 1982:42, fig. 51). The slightly flared blade

Figure 2.13  Fragment of a sandstone bivalve mold half for the casting of a small socketed implement, perhaps an adze/axe. The exterior surface of the mold half has an “X” incised in it. Mold marks are also found on ceramic bivalve molds excavated from 1st millennium B.C. copper-smelting sites of the KWPV of central Thailand. (See Fig. 2.18.)

shape with faceted lateral edges on one blade face is very similar. The Phu Lon example is a little larger (2 cm longer) and has a cast-in indentation in the socket rim on the side with facets along the blade sides. In addition, the top of the Phu Lon socket is bowed whereas the top of the Ban Chiang socket is flat. Nevertheless, a typological link to sites in the Sakon Nakhon Basin and perhaps elsewhere in the Mekong Basin may be suggested.

The Phu Lon Complex in Regional Context Four archaeological projects have conducted site surveys in various parts of Loei Province: the Pa Mong Archaeological Survey Programme (1973– 1975) team directed by Donn Bayard (Bayard 1980), James Penny’s 1977–1978 field survey (Penny 1986), Somsuda Rutnin’s (1988) 1983–1985 survey, and the TAP 1984 survey (Natapintu 1988; Pigott 1984, 1985; Pigott and Natapintu 1988:156–159, 1996–97:787–794; Pigott et al. 1992). None of these surveys uncovered evidence in Loei Province for long-term prehistoric human settlement on any scale or density comparable to, for example, the upper Songkhram/Khumpawapi area, where the Ban Chiang cultural tradition’s sites are located. However, test excavations associated with the surveys showed that the occupation of the greater Loei region seems

PREHISTORIC COPPER MINING AND SMELTING

to have intensified significantly over the course of the 1st millennium B.C. and more particularly during the iron period. Bayard’s survey in northern Loei and along the Mekong did identify 13 prehistoric open-air and cave sites. He tested a handful of sites and found no evidence of copper/bronze but did find a copper/bronze bar at Tham Din on the Lao side of the Mekong opposite Nong Khai Province (Bayard 1980:96, 141). Penny located a few occupation sites among at least 14 prehistoric sites in southern Loei Province and more in Khon Kaen and Chaiyaphum provinces immediately to the south. He test excavated three 1st millennium B.C. to early centuries A.D. occupation sites, two in southern Loei, Ban I Loet and Ban Puan Phu, and one other, Non Khaw Wong, in Khon Kaen Province. The pottery from the sites shows strong similarities to Don Klang iron period pottery (Joyce White, pers. comm. 2018). All three sites tested by Penny were found to have evidence for copper/bronze processing in the form of crucible and copper-base metal fragments (Penny 1986:110– 152). These sites, which Penny tested as part of his investigation of what he termed the Phu Kradung ceramic tradition, must be included, along with the sites of the Ban Chiang cultural tradition in the Sakon Nakhon Basin, among the logical candidates for the exploitation of Phu Lon Complex’s resources and the processing of ores and/or metal. The Penny sites all lie on the Khorat Plateau but are well to the south and east of the Phu Lon Complex. Rutnin’s 1983–1985 survey (Rutnin 1988) concentrated on Loei and contiguous portions of adjacent provinces and located 61 sites. Her test excavations at two sites in Loei revealed (1) an iron period occupation at the open-air site of Non Phrik (ca. A.D. 300–400); and (2) a second site of Pha Phim cave, with evidence of use at a time equivalent to Ban Chiang lower Early Period. Four iron artifacts from Non Phrik were analyzed metallographically by L. M. Hogan (Hogan 1996–97; Hogan and Rutnin 1989). In western Udon Thani Province, Rutnin also excavated the stone adze/axe production site of Non Sila of probable iron period date (Rutnin 1988). In the TAP 1984 survey in the region of northern Loei, the most important prehistoric site documented was the Phu Lon Complex. Although the Phu Lon Complex is the only known prehistoric

21

mining and smelting site thus far located in northeast Thailand, sites in neighboring provinces to the east and south (see TAM 2A, fig. 1.1, and Figure 4.1 in this volume) contain evidence of extensive metal product manufacturing. From the quantity of tin bronze artifacts known from numerous prehistoric sites on the Khorat Plateau, it is possible that additional local ore sources at currently unidentified locations (not only the Phu Lon Complex) may have been supplying these settlements with raw materials and/or metal over time. However, economic geological surveys in Thailand thus far have not documented other copper deposits with substantial evidence of ancient workings. SEALIP research (e.g., Pryce 2012a; Pryce et al. 2011a, 2011b, 2014; see Chapter 3 in this volume) is furthering understanding of possible connections (or lack thereof ) between known ore sources and excavated copper-base artifacts. The LIA signature of the tin bronze socketed axe (SEALIP/TH/PL/10) from the Phu Lon Complex Ban Noi locus suggests that its signature is compatible with that of clusters of wires found in burials in Myanmar (Dussubieux and Pryce 2016:611–612, fig. 12). As these authors note, “this data correspondence represents one of the first solid links between prehistoric Myanmar and Thailand and may suggest land-based, intermontane exchange between the two regions (Dussubieux and Pryce 2016:611–612). Thus far, LIA analyses of metals from sites in northeast Thailand do not share the Phu Lon Complex’s isotopic signature. That the sizeable SEALIP program so far has not demonstrated who the main consumers of Phu Lon copper were may result from possible recycling of copper/bronze objects, which may be masking the Phu Lon lead isotopic signature. However, as mentioned above, SEALIP did strongly suggest the on-site production of tin bronze and its probable casting in the form of the Ban Noi socketed adze/axe. In northeast Thailand, the strongest evidence to indicate that its geographically distant settlements were in contact and linked technologically during prehistory is the shared common technological tradition found in the manufacturing of crucibles. Vernon analyzed the crucibles from the Phu Lon I loci (Vernon 1996–97) and those from Ban Chiang, Ban Phak Top, Ban Tong, and Don Klang (Vernon 1997; see TAM 2B, chapter 5). Although no intact crucibles were excavated at the Phu Lon Complex, and

22

2C: METAL REMAINS IN REGIONAL CONTEXT

the crucibles there were smaller, its crucible sherds resemble those from Ban Chiang and related sites in their morphology as well as in the technological system of their manufacture (see TAM 2B, chapter 5; Vernon 1997). Both the Phu Lon Complex and the Sakon Nakhon Basin crucible sherds often show the presence of a thin, lagged layer (see TAM 2B, chapter 5, and fig. 5.3, color figs. 5.4 and 5.5) lining the bowl of the crucibles. These layers of lagging, first identified at Phu Lon by Vernon, have now been noted at Ban Non Wat in the upper Mun Phimai region of southern northeast Thailand (Cawte 2012:461–462). As discussed in TAM 2B, chapter 5, this layer of lagging is composed of a highly refractory, finely crushed quartz slurry that had been applied to the crucible interior after firing. The lagging enables the crucible to survive the thermal stresses of melting/smelting metal, retards erosion of the crucible wall as well as metal loss into its fabric, and allows multiple reuses of the crucible. This lagged layer is quite a specific technological commonality and suggests shared knowledge and probable cultural contact among sites where it appears (see Pigott 1998:214–215). Differences in temper used, clay, and vessel size suggest that there was no uniform recipe for crucible manufacture nor a single center for crucible manufacture. What is consistent among these sites is the choice of a basic shape of a relatively small crucible vessel with pouring spout and the application of lagging to the crucible’s interior. Such crucibles had rims that were either tapered or rounded, but no distinction in function was apparent between them (Vernon 1996–97:810, plate 2). The mineral suites represented in the Phu Lon Complex crucibles indicate that those crucible sherds analyzed petrographically were made on or near the site from local clays (Vernon 1996–97:811–814).

Central Thailand: The Lopburi Region The Lopburi region of central Thailand has also been explored as a potential source area for some of the copper in artifacts excavated at sites on the Khorat Plateau of northeast Thailand. Thus far, two locations in Lopburi have revealed evidence for prehistoric mining and smelting: the KWPV and the neighboring KSOMD (Fig. 2.14). There are several

documented copper ore sources in the KWPV and immediate vicinity (Bennett 1989:331–334; Natapintu 1988:115, table 2; Vernon 1988), plus at least one small copper ore outcrop documented near the neighboring Khao Sai On site (Ciarla 2007b:398– 400 and fig. 5; Cremaschi et al. 1992). These deposits are primarily of the weathered, copper sulfide orebody type, as at the Phu Lon Complex, and would have offered a variety of copper ores from surface-exposed oxide and carbonate ores (e.g., malachite, chrysocolla, azurite) to deeper-lying sulfides (e.g., chalcopyrite). Unlike the Phu Lon Complex, the archaeological sites associated with Lopburi regional copper production have clear evidence of both copper production and occupation. The KWPV’s copper production evidence came to light as a result of a site survey and excavation conducted on the Lopburi Plain by Surapol Natapintu for the Central Thailand Archaeological Project (CTAP) of the Thai Fine Arts Department (e.g., Natapintu 1984a, 1984b, 1988:107–108). Three sites were investigated subsequently in the KWPV by TAP under the co-direction of Natapintu and the author: Non Pa Wai, Nil Kham Haeng, and Non Mak La. Both Non Pa Wai and Nil Kham Haeng are prehistoric copper production sites approximately five or more hectares in size, and they rank among the largest single locus prehistoric copper smelting sites known in Eurasia. The preliminary results from the current TAP AMS 14C dating program combined with earlier TAP 14C dates and ceramic analysis suggest a later 2nd millennium B.C. date for the advent of copper smelting and casting at Non Pa Wai (Rispoli et al. 2013:109, fig. 4, 125). Production here, as at Nil Kham Haeng was pursued intensively during the 1st millennium B.C. (see Table 2.2). Rispoli et al. (2013) did argue that production at the latter site continued into the early 1st millennium A.D., however, the new dating program has yet to shed any new light on this possibility. Sites comparable in size to those in the KWPV might include the massive slag heap (an estimated 400,000 tons) associated with the 1st millennium B.C. copper mining site of Tonglüshan near Wuhan in Hubei Province, China (e.g., Vogel 1982; Zhou et al. 1988). Unfortunately, this slag heap has been bulldozed and is no longer available for study. In central Laos at Sepon, though several mines have

PREHISTORIC COPPER MINING AND SMELTING

Figure 2.14  Map of the Lopburi Region Transect (LRT) including the two study areas in central Thailand, the KWPV and the KSOMD. Adapted from Rispoli et al. (2013, fig. 1).

23

500 B.C.

600 B.C.

700 B.C.

800 B.C.

Short Dvaravati presence

Cu production & occupation have wound down?

Industrial Deposit Peak Cu smelting period begins

Founder’s burials

Hiatus?

Initial occupation

Non Pa Wai

Cu production & occupation have wound down?

Cu smelting begins Intensive Cu production begins

Nil Kham Haeng

Occupation has wound down?

Metal Age occupation begins, some small-scale Cu production

Initial occupation

Non Mak La

Occupation & Cu production begin Occupation & Cu production end in early Protohistoric period. Small village A.D. 600–1000

Cu production ends in early Protohistoric period

Noen Din

Cu production begins

Khok Din

Khao Sai On Mineral District

Note: For a detailed review of the earlier working chronology see Rispoli et al. (2013); see also introduction to this chapter for brief overview of the chronology in transition and of the team responsible for the new TAP AMS 14C dating program.

A.D. 1 –Protohistoric period

200 B.C.

400 B.C.

Hallstatt Plateau

1200 B.C.

1700 B.C.

2300 B.C. 1800 B.C.

Dates

Khao Wong Prachan Valley

Table 2.2  A Revised Working Metallurgical Chronology for the KWPV and the KSOMD Sites

24 2C: METAL REMAINS IN REGIONAL CONTEXT

PREHISTORIC COPPER MINING AND SMELTING

been found at what is termed the Vilabouly Complex, it is not clear how much smelting accumulation is present at this prehistoric copper mining center (Sayavongkhamdy et al. 2009; also Pigott and Pryce forthcoming; Pryce 2012a, 2012b; Pryce et al. 2011a, 2014; Chapter 3 in this volume). The vast mining district of Kargaly in the Urals has hundreds of mine shafts spread over ca. 500 km2, but lacks enormous accumulations of slag, as the ores were moved from the mines to smelting loci some distance away (Kohl 2007:170–178). The third TAP site in the KWPV is Non Mak La, which also has evidence for copper smelting in at least one locus. It is a discontinuous, prehistoric, multi-activity site—e.g., habitation, mortuary, copper and iron smelting (historic)—with a surface scattering of artifacts spread across tens of hectares by plowing. It has well-dated late neolithic occupation from the 2nd millennium B.C. and indications that occupation persisted into the same time frame as Non Pa Wai industrial phase as well as early Nil Kham Haeng in the 1st millennium B.C. There is also evidence for protohistoric activity at the site, including evidence for iron smelting. It remains curious that while in northeast Thailand excavated copper-base artifacts are almost exclusively of tin bronze (see Chapter 4), those in the KWPV and KSOMD, based on current analytical evidence, appear to be mostly of unalloyed copper. However, two tin bronze artifacts are known currently from burials at Nil Kham Haeng, while Pryce et al. (2010:255, table 7) mention the presence of trace levels of tin in the production debris from this site. Therefore, it is important to keep an open mind concerning the possible/probable presence of tin bronze production at sites in the KWPV like Nil Kham Haeng. The late 2nd millennium B.C. date for the advent of copper smelting in the KWPV is consistent with Ban Non Wat’s dating sequence based on evidence of contact between Ban Non Wat in southern northeast Thailand during its phase BA2 (1000–900 B.C.) and the KWPV, to be discussed below (Pryce et al. 2014:292; also Pryce et al. 2010). As it progressed over the course of the 1st millennium B.C., the scale of the KWPV industry was such that it can be concluded that this valley and the KSOMD together comprised a major regional center of copper production and distribution (e.g.,

25

Bennett 1988a, 1988b, 1989, 1990; Ciarla 2007a, 2008; Higham and Rispoli 2014; Natapintu 1987, 1988, 1991; Pigott 1999; Pigott and Natapintu 1988; Pigott et al. 1997; Pryce 2009, 2012a, 2012b; Pryce and Abrams 2010; Pryce and Pigott 2008; Pryce et al. 2010, 2011a, 2011b, 2013, 2014; Rispoli et al. 2013; White and Pigott 1996; see also Table 2.3 for a comparison of mining and metalworking evidence in all the sites discussed in this chapter). The scale of copper production in the KWPV was massive and indicates extraction, smelting, and casting on a level far beyond local consumption. This evidence, in turn, would suggest that raw metal and metal items were being exported, perhaps to sites elsewhere with evidence of copper-base artifact casting, but lacking readily available ore sources or sources of metal. However, it remains the case that until the more detailed analysis of the stratigraphic contexts of the KWPV TAP sites currently underway can be completed, the true nature of their relationship, interaction, and chronology will remain indeterminate.

Non Pa Wai Evidence for Smelting and Casting A total of ca. 570  m3 of site deposit was excavated in 14 operations over two seasons (see Pigott et al. 1997:145, fig. 3). Excavations conducted by TAP at Non Pa Wai in 1986 and 1992 revealed that the site’s considerable volume, at least 5 hectares in horizontal expanse and ca. 4  m at the deepest, is composed primarily of the industrial debris of copper production—gangue/ore fragments, ore crushers, crucible sherds, slag cakes, and ceramic molds— accumulated over centuries of activity (Color Fig. 2.15). Non Pa Wai was occupied at least as early as the late 3rd millennium B.C., as a single, AMSdated millet seed from the neolithic period burial ground, the so-called “Outlier” at plain level at the northwest periphery of Non Pa Wai, provided such an early date (Weber et al. 2010). Additionally, this early date gives support to several previously obtained conventional late 3rd millennium B.C. radiocarbon dates from Non Pa Wai’s basal deposit. As has been mentioned, it is argued that copper production at Non Pa Wai did not commence until

slagged common SE Asian crucibles, some with prills, charcoal, very few identifiable slag fragments

common SE Asian crucible used for melting & casting

Smelting

Metal refining

1 intact smelting crucible recycled as a melting crucible

massive numbers of slagged smelting crucible sherds with no lagging, charcoal, a few chimney sherds, massive slag deposit of intact & broken slag cakes in site fill, possible smelting pit-rims

hammerstones, anvils, coarsely broken host rock/ore fragments in site fill

hammerstones, anvils, malachite ore, finely crushed host rock/ore & possible slag

Ore beneficiation

no evidence at site

copper & iron orebody at Khao Tab Kwai

pits, adits, shafts, galleries, tailings, mauls

Non Pa Wai Main Mound

Nearby ore sources

Mining

Site

Phu Lon Copper Mining Complex no evidence at site

Non Mak Laa

no evidence

large NPW-type slagged smelting crucible sherds but fewer than at NPW, enormous quantity of slag skins, charcoal, intact & fragmentary chimneys, massive deposit of intact, broken & finely crushed slag cakes & slag casts

hammerstones, anvils, numerous lenses of finely crushed host rock/ ore & slag

no evidence

large NPW-type slagged smelting crucible sherds but fewer than at NPW, charcoal, smelting pitrims, intact & broken slag cakes in site fill & an isolated large slag heap, chimney sherds, copper & iron ore fragments; HP: tuyeres, furnace wall linings probably from iron smelting, smithing buns from iron-working

some host rock fragments, small cubeshaped hammerstones

copper orebodies copper & iron orebody at on Khao Phu Kha, at Khao Tab Kwai least 2 large galleries present

no evidence at site

Nil Kham Haeng

no evidence

no evidence

no evidence

open pit copper mine, adit & shaft at higher elevation

Khao Sai On

no evidence

smelting slag, crucible sherds, chimney sherds

hammerstones, anvils, numerous lenses of finely crushed host rock/ore & slag

Khao Sai On mine

no evidence at site

Khok Din

no evidence

Smelting slag, crucible sherds, chimney sherds, slag skins, biconical chimney plugs

hammerstones, numerous lenses of finely crushed host rock/ore & slag

Khao Sai On mine

no evidence at site

Noen Din

Table 2.3  Summary of Evidence for Mining, Copper-base Metal Production, Artifact Casting, and Burials at the Phu Lon Copper Mining Complex, Three TAP Sites in the KWPV, and the Three LoRAP Sites in the KSOMD

no evidence

2 BVM fragments for socketed implements, locally cast tin bronze socketed axe

several discrete areas for mining & ore processing

copper & tin bronze

no evidence of permanent habitation, probably seasonal mining expeditions, domestic pottery sherds

no evidence

Casting ingots

Casting artifacts

Specialized activity areas

Primary metal/ alloy present

Habitation

Burials ca. 18 burials in premetal Main Mound basal deposit ca. early–late 2nd mill. B.C.

domestic pottery sherds, animal bone, basal deposit postholes

some ceramic BVM fragments, 1 cordiform implement, open mold, 1 miscast copper “arrow point”

2 possible cup mold ingots, a few cup & conical molds

no evidence

Non Mak Laa

14 burials mostly ca. 1st mill. B.C.

domestic pottery sherds, animal bone, living surfaces, postholes

56 primary, some secondary, 1 skeleton in CTAP slag heap, site is ca. 2nd–1st mill. B.C.

domestic pottery sherds, animal bone, living surfaces

copper with traces of arsenic; HP: iron

none; site matrix was smelting in at least the homogeneous CTAP slag heap locus

ceramic BVMs for implements & ornaments, copper-base bangles

cup & conical molds for ingot casting but fewer than at NPW, locally cast cordiform copper implements & ingots, disk ingots

trace levels of tin in slag

Nil Kham Haeng

copper (very little mostly copper, 2 excavated), a few iron tin bronze artifacts fragments (imported?), copperbase bangles

none; debris in & across site fill was homogeneous

ceramic BVMs for implements & ornaments, ceramic socket mold plugs

tens of thousands of ceramic cup & conical molds for ingot casting, slag ingot pseudomorphs

no evidence

Non Pa Wai Main Mound

no evidence

no evidence

no evidence

no evidence

no evidence

no evidence

no evidence

Khao Sai On

no evidence

domestic pottery sherds

probably copper

none; site matrix was homogeneous

BVMs, 1 ceramic socket mold plug

1 large cup mold

no evidence

Khok Din

6 burials in 2 mortuary phases, 1 infant with 9 ceramic BVMs

domestic pottery sherds, a few postholes

probably copper

copper smelting area in Northern Trenches

9 exhausted, broken BVMs in infant burial

no evidence

no evidence

Noen Din

Note: LoRap = Lopburi Regional Archaeological Project; TAP = Thailand Archaeometallurgy Project; CTAP = Central Thailand Archaeological Project; BVM = Bivalve mold; HP = Historic Period; NPW = Non Pa Wai; mill. = millennium; SE = southeast. a combined TAP & CTAP excavation data.

tin bronze, copper & tin prills in crucible slag

Phu Lon Copper Mining Complex

Alloying

Site

28

2C: METAL REMAINS IN REGIONAL CONTEXT

the later 2nd millennium B.C. Inhabitants of the KWPV had ample, small, local copper deposits to exploit over centuries of metalworking activity. At this time, while “old workings” are known in the hills surrounding the KWPV, the specific mines that were supplying the ores being smelted at any of the three sites in the valley are as yet undetermined. At Non Pa Wai, visual observation of excavated ore fragments suggests that its inhabitants may have been mining easily accessible copper ore reserves at nearby Khao Tab Kwai (see Fig. 2.14). Malachite, azurite, and chrysocolla are three oxidic ores documented as occurring at both Non Pa Wai and Khao Tab Kwai, which is also a major iron ore (hematite and magnetite) source (Bennett 1989:332). All of the 18 confirmed burials on the Main Mound at Non Pa Wai were located in the site’s basal deposit. Three contained copper-base metal and two each contained a pair of bivalve molds for casting large socketed adze/axes. These molds are decorated on the interior with two pairs of incised bands set several centimeters apart, which would have resulted in pairs of distinctive bands in relief on the exterior of the cast adze/axe. From their deep-lying location in the mound’s basal deposit and from the artifacts they contained, the four burials are interpreted as relating to the initial phase of metallurgical activity in the KWPV, i.e., the late 2nd millennium B.C. (Table 2.2). The copper-base artifacts in burials included: an amorphous artifact, a fish hook, and a socketed copper-base adze/axe. This latter artifact by PIXE analyses conducted under the author’s auspices through MASCA was demonstrated to contain ca. 0.75 wt% tin (Pigott et al. 1997:122). Subsequently, it was subjected to LIA by SEALIP (SEALIP/TH/NPW11). Its LIA signature suggested it did not share a common signature with other samples tested from the KWPV, and hence it was probably not cast from KWPV copper (see discussion in Pryce et al. 2011b:154–155; Pryce et al. 2014:292, table 1 on page 280, table 2 on page 285). The current supposition is that it was an imported artifact and that as such it may have played a role in stimulating KWPV’s primary copper production (Pryce et al. 2011a:3310, 3315, fig. 7, 3320; for an extensive discussion of this socketed adze/axe and typological comparanda, see Ciarla 2007a; Higham and Rispoli 2014:12 and fig. 7; Higham et al. 2011a; Pigott and Ciarla 2007). The fish hook was interred along with

Figure 2.16b  Broken but complete ceramic bivalve mold pair for the casting of a large, deep socketed adze/axe from the “Grave of the Metalworker” at Non Pa Wai (see also Color Figs. 2.16a and 2.18). (Scale = 10 cm.)

a fragmented pair of ceramic bivalve casting molds for a large socketed adze/axe (Color Fig. 2.16a and Fig. 2.16b; see also Pigott 1999:13, fig. 5). Notably, two copper-base adze/axes from Ban Non Wat phase BA1 (burials 470 and 572) are argued to be typologically similar to these Non Pa Wai burial bivalve molds (Higham and Rispoli 2014:12 and fig. 7). Such burials with molds are referred to as “founder’s burials” or by some as “smith’s graves,” given the presence of “tools of the trade.” Some of the burials in the compact, ca. 50 cm deep basal deposit at Non Pa Wai are interpreted as neolithic period based on the presence of chipped and groundstone adze/axes found in association with neolithic period pottery, marble disc-shaped pendants, disc and H-shaped beads, and freshwater bivalve shells (Higham and Rispoli 2014:6–10; Rispoli et al. 2013:115–119). Some burials from this same basal context contained no artifacts and remain undated, while the five burials with copperbase artifacts and/or manufacturing equipment are interpreted as bronze period. However, it is clear that at Non Pa Wai, its shallow basal deposit has an overlying caliche layer of variable thickness. Caliche forms when calcium carbonate precipitates in sediments under conditions of strong leaching in arid

PREHISTORIC COPPER MINING AND SMELTING

conditions. It can occur at or near soil surfaces, but also it can precipitate beneath soil surfaces even at a depth of several meters. This layer is also found at other sites in the Lopburi region, including neighboring Non Mak La and more distant Tha Kae (Cremaschi et al. 1992; Rispoli et al. 2013:134). In the basal deposit, the task of isolating bronze period metallurgical production remains (e.g., crucible sherds, slag, etc.) proved difficult because of intrusive metallurgical remains from the Industrial Deposit immediately above the basal deposit. Pitting and other anthropogenic disturbances from this deposit penetrated through the caliche layer into the underlying basal deposit creating a potential for mixing Industrial Deposit materials with those in the underlying basal deposit. Only a more detailed reanalysis of the excavation records along with the artifacts and their contexts may offer an improved level of understanding of this stratigraphically complex basal deposit. However, TAP investigators believe that some basal deposit smelting remains, such as pit-rims and a nearly intact crucible, derived from bronze period metalworking activities. The shallow basal deposit at Non Pa Wai is overlain by a two-meter-thick Industrial Deposit that dates mainly to the 1st millennium B.C. (see Color Fig. 2.15 and Table 2.2). This Industrial Deposit is characterized by a fine, ashy soil matrix that has been heavily disturbed by bioturbation and human activity and is filled with slag, ore and host rock fragments, and ore crushing tools. Ceramics included domestic potsherds, smelting crucible sherds, bivalve casting molds for various ornaments and implements, and intact and fragmentary cup and conical molds, possibly for the casting of ingots (Figs. 2.17, 2.19, and Color Fig. 2.18). A number of the bivalve, cup, and conical molds were marked with curvilinear and geometric designs (e.g., Natapintu 1988:119, figs. 11, 12; Pigott 1999:17, fig. 12; Pigott and Natapintu 1988:160–161, figs. 14.3–14.5, 1996–97:801, figs. 7–9; Pigott et al. 1997:150, fig. 12). The purpose of the designs remains undetermined, although it is possible that they were makers’ marks of some sort. The evidence at Non Pa Wai for human habitation during the rapid accumulation of the Industrial Deposit consists of large quantities of domestic potsherds and faunal remains, but not burials or living floors, so it is not clear if metalworkers resided on site full-time or just seasonally.

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Figure 2.17  Illustration demonstrating the range of typological variability in ceramic cup and conical ingot-casting molds found at Non Pa Wai, Nil Kham Haeng, and Non Mak La. Adapted from Armstrong (1994).

Figure 2.19  Example of a marked ceramic thick-butted, shallow mold (T#8501), ca. 10 cm high.

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The matrix of Non Pa Wai’s Industrial Deposit is remarkably homogenous across the site’s ca. 5 hectares (Pigott et al. 1997:145, fig. 3). The manufacturing byproducts and discarded production equipment at the site amount to thousands upon thousands of tons of debris, all evidence of prehistoric copper smelting and casting on a significant scale over many centuries. Detailed microstructural and microanalytical data on the main classes of smelting remains from both Non Pa Wai and Nil Kham Haeng have provided important insights into the technique and precision of the technological system involved (e.g., Pryce 2009; Pryce et al. 2010).

smelting at non pa wai The majority of the analyzed evidence for smelting at Non Pa Wai derives from the Industrial Deposit. In addition to the characteristics of the Industrial Deposit described above, three classes of artifacts document the nature of the smelting technological system employed at the site: crucibles, slag cakes, and perforated cylinders also known as chimneys. Smelting was conducted in large ceramic crucibles judging from the size of the generally heavily slagged crucible sherds as well as the one intact crucible excavated from a bronze period basal deposit context (Color Fig. 2.20; see also Pryce et al. 2010:247, fig. 4). These crucibles were larger and of a distinctly different shape than “the common Southeast Asian crucible” as described by White and Hamilton (2009:365–367) and which are frequently found at sites in northeast Thailand. The crucible sherds, which must number in the tens of thousands in the site, were excavated from the Industrial Deposit and are consistent in size, shape, and fabric with the intact crucible, so the interpretation that follows is considered applicable to Non Pa Wai’s entire copper production temporal sequence as well as its chaîne opératoire. The intact crucible (roughly 17 cm wide and 8 cm high) is unusual as post-manufacture modifications indicate that it had been reused. The rim was carefully chipped from the top towards the exterior resulting in an outward-slanting lip with semi-circular indentations used possibly for the pouring of molten metal. A larger break at one point in the crucible rim would also have served as a spout for pouring molten

metal. Several other crucible sherds show the same treatment suggesting crucible reuse was at least occasionally undertaken (Fiorella Rispoli, pers. comm.). This larger, distinctive form of crucible appears to have been used from the outset of copper smelting at Non Pa Wai, as additional crucible sherds of the same type were found in the basal deposit context as well as in the Industrial Deposit. Thus, this crucible technology persisted over the centuries of production at this site. The crucible sherds are uniformly shaped and are heavily tempered with quartz and organic chaff, perhaps from rice plants (Pryce et al. 2010:247). The crucibles are not spouted or lagged and, except as noted above, most of them show no signs of reuse. The excavators found no activity areas devoted specifically to crucible manufacture. No unambiguous smelting installations in the Industrial Deposit were documented, although in the basal deposit there appear to be some metallurgy-​ related features. The fine, loose, powdery nature of the soil matrix in the overlying Industrial Deposit did not facilitate the preservation of features of any sort, including clearly defined stratigraphy. Installations could easily have been degraded by weather and contemporaneous human and animal traffic on the site. The basal deposit of the site that contained the mortuary features was dark brown, relatively compact, and preserved features better than the upper Industrial Deposit. In this basal context there were indications of production, namely a few fragmentary, slagged crucible bases plus the single nearly intact crucible found in situ. The site’s crucible assemblage is in need of detailed review, but at this juncture the excavators speculate that a similar crucible type is found throughout the entire Non Pa Wai sequence (Roberto Ciarla and Fiorella Rispoli, pers. comm.). Other associated evidence in the basal deposit includes an in situ shallow pit ringed with a thick, terracotta rim, a so-called “pit-rim” that may have held a smelting crucible during heating. Pit-rim fragments were also excavated from this context. A sketch of such a possible smelting pit, about 20 cm in diameter, with a squat ceramic rim is found in Ciarla’s 1986 excavation notebook. It was reproduced by Pryce (2009:125, fig. 5.5), who noted that it is similar to constructions described by Craddock (1995:133) at Los Millares in Iberia and by Golden et al. (2001) at Shiqmim in Israel. Pryce et al. (2010:247) suggested, in regard to these possible smelting pits, that “[t]hese

PREHISTORIC COPPER MINING AND SMELTING

low-profile structures might allow a deeper charcoal bath, but they cannot be thought of as furnaces in the sense of encouraging updraft, facilitating very high temperatures and/or very low partial pressures of oxygen (e.g., Merkel 1990; Pryce et al. 2007).” The pit-rims are made of the same distinctive grit-tempered ceramic fabric as found in the rare perforated cylinder or chimney sherds, which are present at Non Pa Wai in the Industrial Deposit only (cf. Pryce et al. 2010:247–249; see also Bennett 1989:344). These perforated cylinders and fragments also are found in founder’s burials (see Frontispiece) as well as floating in site fill at Nil Kham Haeng and the KSOMD sites (Ciarla 2008:331–335; Pigott et al. 1997:130–132; Pryce et al. 2010:247–249; Rispoli et al. 2013:139). In the TAP excavation record and in previous publications, they have often been termed “furnace chimneys” or “chimneys.” They can be described as short, cylindrical, perforated stacks often with eight ventilation perforations. The example T#5347 (see Color Fig. 2.21), excavated from a Nil Kham Haeng burial, stands ca. 15 cm high, with a ca. 26 cm exterior diameter, ca. 18 cm interior diameter, and ca. 4 cm thick walls made of a grit-tempered fabric, which often has a characteristic oxidized, reddish-orange color from repeated reheating. The chimney sherds excavated in the site fill were not found in situ in functional contexts, so there are no clear indications of their exact role. However, from the excavation of broken but complete examples in burials at Nil Kham Haeng, it is known that these cylinders were made to a basic, standardized shape and size. The first hypothesis presented for the use of these cylinders was that, if placed atop a stabilized smelting crucible set in a pit, the crucible and cylinder together might have served as a portable furnace, i.e., one that could be dismantled and moved elsewhere to be used. The perforated chimney would have admitted a natural or bellows air draft to drive the smelt and concentrated hot smelting gases in an updraft (Pigott et al. 1997; cf. Pryce et al. 2010:249 and fig. 5). However, smelting experiments conducted by Pryce using this “portable furnace” reconstruction resulted in the consistent slagging of the interior of the cylinders. No excavated KWPV cylinder, intact or fragmentary, shows indications of slagging. Thus Pryce argued that the cylinders may not be have been used in smelting processes (Pryce

31

2009; Pryce et al. 2010:249; cf. Ciarla 2008). Nevertheless, the grit tempering and the fact that they are hard baked to orange color probably from repeated firings strongly suggest that the cylinders were somehow part of a pyrotechnological process, most likely one metallurgical in nature, especially given their recovery from metal-producing contexts. Perhaps they could have been used, for example, to hold crucibles charged with metal and charcoal for the process of melting copper. At present, however, although their true function remains open to debate, the perforated cylinders are termed hereafter as “chimneys” for the sake of a convenient nomenclature. A byproduct of the smelting process and a common find in the Industrial Deposit at Non Pa Wai is the so-called slag cake. After each smelt, it appears that the molten slag in the crucible was poured onto the ground, forming a plano-convex, thick, circular mass of slag (Fig. 2.22a, Color Fig. 2.22b). Much of Non Pa Wai’s massive slag accumulation in the Industrial Deposit comes from the breaking up of these slag cakes. The excavation of a single 5 x 5 m

Figure 2.22a  Typical surface find example of a plano-convex slag cake from Non Pa Wai. Note ropy upper surface resulting from pouring molten slag from smelting crucible.

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square (TAP 1986, Op. A) in the Main Mound’s Industrial Deposit, ca. 2 m thick, yielded ca. 1000 kg of slag. These cakes seem to have been broken up purposefully, perhaps to assess how much copper remained trapped in the slag and for possible recycling of residual copper during subsequent smelts. The high volume of slag from Non Pa Wai is probably related to the types and mixtures of ores being smelted and the specific smelting procedure employed. That oxidic and sulfidic ores were being co-smelted at Non Pa Wai has been demonstrated by Pryce’s research (Pryce et al. 2010:253, 261), and this process tends to produce considerable slag (Rostoker et al. 1989).

non pa wai: ingot casting What was done with the copper smelted at Non Pa Wai? The best understanding of this comes from the massive Industrial Deposit that makes up most of the site itself. Tens of thousands of fragmentary and intact ceramic cup and conical molds are concentrated in this deposit (Pigott et al.1997:149, fig. 11; see also Pigott 1999; and see Fig. 2.17). The size, shape, and quantity of these molds suggest that they were used to cast ingots. Thus Non Pa Wai was the locus of long-term, high-volume production of copper, in particular portable copper ingots cast in these ubiquitous molds. Raw copper was being smelted and cast into a variety of ingot shapes, most of which are relatively small, portable, and appropriate for trade and exchange. Despite the large numbers of cup and conical molds, no actual ingots were excavated at this site. Neither is there evidence of finished metal products in tin bronze or their manufacture at Non Pa Wai. These ingot molds are thus far unique, at least within Thailand, to sites in the greater Lopburi region, with the greatest concentrations in the KWPV, with some found also in the KSOMD. Non Pa Wai: Ingot Production From the debris found at Non Pa Wai, initial hypotheses were developed about the technological system for ingot production (e.g., Pigott 1998; Pigott and Natapintu 1988; Pigott et al. 1997). The hypothesized reconstruction for the chaîne opératoire begins with a smelting crucible filled with molten copper and slag, a smelt at completion. A thick top

layer of slag, floating above a pool of molten copper, would have been evacuated from the crucible by the metalworkers, perhaps into a depression in the ground, forming one of the ubiquitous slag cakes. These plano-convex cakes, typically ca. 15 cm in diameter, ca. 5.5 cm thick, and weighing as much as 1.5 kg intact, were found at times with potsherds stuck in their convex bottom surfaces, probably a result of the molten slag being poured onto the sherd-littered site surface (Pryce et al. 2010:249–251 and fig. 6; see also Bennett 1989:338). In order to produce a casting, not all the molten slag would have been poured from the crucible’s interior as some semi-molten residues remained afloat on the surface of the molten copper at the bottom of the crucible. The next step involved pouring the molten copper into aligned cup molds as quickly as possible. The flat-bottomed cup molds would rest solidly on the ground whereas the conical molds could have been wedged firmly by their tapering ends into the soft soil of the site’s surface. This process would not have been easy and would have required practice, as all pouring appears to have taken place directly from smelting crucibles that apparently lacked pouring spouts. There is no indication of how the extremely hot crucibles were handled during pouring. Perhaps the crucible could have been pinched between two long green bamboo poles held by a person at each end. As mentioned above, only one intact example of a crucible with a crudely formed pouring spout was recovered. This spout was made simply by breaking away the entire upper rim of a smelting crucible and then breaking open a “spout” in the rim wall (see Color Fig. 2.20; see also Pryce et al. 2010:264, fig. 3). If this were a typical melting crucible at Non Pa Wai, it would have made for crude and imprecise pouring. Controlling the pour from a typical spoutless crucible must have been difficult, and towards its completion it would not have been possible to stop the remaining molten slag in the crucible from pouring into the last molds in the row. Workers continued to pour quickly until the crucible was empty in order to cast all available copper. Such slag pours resulted in the formation of slag pseudomorphs of copper ingots (Fig. 2.23a, b). A flat-topped pseudomorph was shaped like an inverted cone because it was cast in an ingot mold with tapering interior walls. As it cooled, the slag would have contracted away from the walls of the

PREHISTORIC COPPER MINING AND SMELTING

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Figure 2.23b  A slag ingot pseudomorph from Non Pa Wai. This artifact was created when the remaining residue of slag in a smelting crucible was emptied into a waiting cup mold. Figure 2.23a  Typical ceramic cup mold for casting a copper ingot from Non Pa Wai.

mold and could easily have been popped out. One would assume the same would apply to metal ingots; but frequently the walls of cup molds are notched or broken almost in half. This fracture pattern suggests that it was often necessary to crack the wall open to remove the metal ingot, perhaps by inserting a pointed implement into the mold between the mold wall and the ingot and levering it out.

Casting experiments conducted by TAP at a local Lopburi-based foundry in 1994 using a typical ancient conical mold successfully produced ingots (Fig. 2.24). Interestingly, ancient cup and conical molds often have an apparent “watermark” on their interior walls indicating the level the molten metal reached inside the mold. In the Lopburi casting experiments a similar but new watermark was observed to form in the mold used.

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Figure 2.24  Ingot resulting from an experimental casting at a local foundry in Lopburi, Thailand. The conical mold was a surface find from Non Pa Wai. Note the “watermark” inside the casting depression in the mold. The modern watermark matched the ancient mark that is still clearly visible.

non pa wai: casting finished products At Non Pa Wai, finished products were cast in ceramic bivalve molds. There are two genres of these: the earlier (basal deposit/bronze period) larger mold type for casting only adze/axes and the later smaller molds. The later, smaller ceramic bivalve molds fall into three basic categories: those for casting personal ornaments such as bracelets, those for casting implements including points and arrowheads, and those for casting small socketed and non-socketed items of unknown function. No stone bivalve molds are known from the KWPV or greater region. Two bronze period founder’s burials from the basal deposit at Non Pa Wai contained pairs of ceramic bivalve molds for casting large socketed adze/axes. These artifacts are the earliest bivalve molds documented in the KWPV and perhaps in Thailand. (For a discussion of these bivalve molds and their comparanda, see Ciarla [2007a:312–319]; Higham et al. [2011a]; Pigott and Ciarla [2007:82–85].) One can speculate on how the deep socket in these bronze period adze/axes was formed based on the identification in the Industrial Deposit of somewhat fewer than 50 examples of

ceramic mold plugs, also known as suspended cores (see Rispoli et al. 2013:127, fig. 15, 1–4). These mold plugs have not been studied in relation to the known bronze period bivalve molds from Non Pa Wai, but these bivalve molds would have required such an artifact to produce their deep sockets. These mold plugs appear too large to have been used with the smaller ceramic bivalve molds excavated in the hundreds of intact and fragmentary examples from the Industrial Deposit (see Color Fig. 2.18). However, it is doubtful that they were churned up from the bronze period basal deposit and, therefore, they may relate to an as yet unidentified type of bivalve mold. From the quantity of Industrial Deposit bivalve molds, ca. 500 documented intact and fragmentary examples excavated from ten 5 x 5 m (or smaller) operations on the Main Mound at Non Pa Wai, it appears that cast artifacts were being produced in quantities meant for distribution to consumers elsewhere. This conclusion is based in part on the lack of finished products in metal at the site as well as on the quantities of bivalve molds that likely exist across the site’s ca. 5 hectares. An intriguing feature of the later smaller bivalve molds is that, like many examples of ingot molds, they also are marked on their exteriors with curvilinear and geometric incised designs (Natapintu 1988:119, fig. 12; Pigott 1999:17, fig. 12; Pigott and Natapintu 1988:160, fig. 14.3, 1996–1997:801, figs. 7–9; Pigott et al. 1997:150, fig. 12). These designs could be a form of maker’s mark to identify ownership or they could perhaps even be marks by which to mate mold pairs together visually prior to casting. The only other site in Thailand where a fragmentary, marked bivalve mold for a socketed implement was found was on the Pottery Flat at Phu Lon I; it does not closely resemble the bivalve molds known from the KWPV in shape or type and it is made from sandstone. Outside of mainland Southeast Asia, marked bivalve molds have been described from the ca. 4th century B.C. site of Yuanlungpo in the Lingnan region of southeastern China (Ciarla 2007a:313; Pigott and Ciarla 2007:83, fig. 10a, 84). Non Pa Wai: Mold Plugs As mentioned above, at Non Pa Wai bivalve mold pairs for deep-socketed adze/axes were found in the two bronze period founder’s burials. A copperbase socketed adze/axe occurred in another contemporaneous burial. For metalworkers to produce a

PREHISTORIC COPPER MINING AND SMELTING

hollow or blind, deep socket by which an implement can be hafted, some form of suspended core casting technological system had to have been used. As also mentioned above, in the excavation of Non Pa Wai’s Industrial Deposit, ceramic, tongue-shaped suspended cores or mold plugs were found (Fig. 2.25). Although the excavated mold plugs are heavily worn or fragmentary, they do illustrate the presence of the practice of socket making for blind sockets of any size. Their worn and often incomplete nature makes associating them with particular mold types difficult. New evidence in this regard may surface when the study of the excavated KWPV bivalve molds is completed. These cores would have been sandwiched in place between the bivalve mold halves, thus suspended by the wider top end of the mold plug. A vertical groove had been carved or shaped into each side of the mold plug’s top end so that, in one potential casting scenario, molten copper could be poured into the bivalve mold pair along the grooves. It is of interest that mold plugs are known not only from the Industrial Deposit at Non Pa Wai and KSOMD sites in the Lopburi region, but also from Ban Non Wat in the Mun Valley, where they occurred in the hundreds in iron period levels. Thus, the occurrence of mold plugs in central Thailand and upper Mun Phimai sites in southern northeast Thailand is another example of a technological link between these two regions of prehistoric Thailand (Higham and Rispoli 2014:13–14, fig. 9). Equally interesting are the occurrences of similar mold plugs in the mid-2nd millennium Erligang metallurgical tradition of China’s central plain (Ciarla 2013: figs. 1.27–1.28; also see Liu and Chen [2012:283, figs. 8A.2, 5] for two different examples of mold plugs from the Nanguanwai foundry excavated at Zhengzhou in Henan Province). A somewhat later example comes from northwest China, a unique specimen of a mold plug and the bivalve mold pair into which the plug fits (seen by the author on a 2011 visit to China). These artifacts were excavated at the site of Huoshaogou in Yumen County, Gansu Province and date to the Shanma Period ca. 1000 B.C.

non pa wai: production of copper-base metal artifacts Recovery of finished copper-base products or even fragmentary pieces of such metal in the basal

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Figure 2.25  Top and side views of a ceramic mold plug or suspended core from Non Pa Wai. This artifact was suspended between the two halves of a bivalve mold pair to create a deep socket in the item being cast. The side view of the plug shows grooves on either side of the upper end of the artifact. The grooves may have been to allow the entry of molten copper and/or to vent hot gases during casting.

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deposit was extremely uncommon at Non Pa Wai. In the Industrial Deposit, there were only a few metal artifacts floating in the site fill (Rispoli et al. 2013). A few fragments of iron were recovered but are of uncertain context or function. Amorphous copper pieces that might have been casting spillage were nonexistent at Non Pa Wai, unlike their frequent recovery at Ban Chiang tradition sites (see TAM 2B, chapters 3, 6, and 7). Despite the quantities of cup/conical molds in the Industrial Deposit, no ingots were excavated at Non Pa Wai. The only two possible small cup mold cast ingots excavated by TAP came from presumably occupational site fill at neighboring Non Mak La, which is only several hundred yards to the southeast (Fig. 2.26; see also Pigott 1999:18, fig. 15). The near absence of excavated metal at Non Pa Wai is remarkable, given its ca. 5 hectares expanse and massive quantity of metalworking debris, and it is suggested that the metal must have been meticulously garnered and moved out of the KWPV to local and regional consumers in both ingot and finished artifact form.

non pa wai: comments on the copper production process Slag analyses have shown that metalworkers at Non Pa Wai were co-smelting oxidic and sulfidic copper ores in crucibles at temperatures in the range of ca. 1240°C, a process characterized as “serendipitous co-smelting” (Pryce et al. 2010:256). It was based on a process of trial and error that was both “inefficient” and “non-standardized” (Pryce et al. 2010:261). These conclusions are built on Pryce’s analyses that show that Non Pa Wai slag has a high chemical variability and that much copper remained trapped in the slag. Copper loss into the slag was seen to be both “elevated” and “variable,” and this loss would have been caused, in part, by an abundance of unreacted ore minerals, some of which were sulfidic (Pryce et al. 2010:251, 253). Copper trapped in the slag was finely disseminated and not in macro-prill form. Fine crushing of the slag, as at Nil Kham Haeng, would not have yielded quantities of prills that could be melted down. To recycle trapped copper the metalworkers would have had to resmelt the slag. There are no indications as to whether or not they practiced slag recycling, but evidence shows that the slag cakes were being

Figure 2.26  One of two cast copperbase ingots (T#18769) excavated at Non Mak La and thought to have been cast in a cup mold. These are the only examples of this type of ingot excavated in the KWPV.

fractured into smaller pieces quite regularly, perhaps for “quality control.” Thus, the slag cakes constituted a potential copper source given the amount of copper trapped in the slag (Pryce et al. 2010:256). The ore mixtures in evidence were a result of the haphazard selection by miners of mixed copper ores that occur in local, weathered, heterogeneous copper sulfide orebodies. Co-smelting obviates the adverse effects that sulfur has on the smelting product when sulfide ores alone are smelted (see Rostoker et al. 1989:85). Without pre-roasting sulfidic ores to drive off the sulfur, smelting such ores does not yield copper in a single, direct step, as does cosmelting. Thus, although the co-smelting may not have been intentional and Non Pa Wai metalworkers might have been unaware of the benefit of mixing oxides and sulfides, they were doing so all the same, using all ores available in the local deposits and increasing their smelting efficiency by doing so. The smelt at Non Pa Wai was probably driven by charcoal made from local vegetation (e.g., bamboo, oak-dipterocarp), but co-smelting can be driven by dry wood fuel alone (Rostoker et al. 1989). The slag from Non Pa Wai is characterized by more abundant residual minerals trapped in the slag than in slag analyzed from the neighboring site of Nil Kham Haeng (Pryce et al. 2010:251). The minerals in the Non Pa Wai slag included fragments of unreacted copper ore and the iron oxide magnetite. At this time, it remains unclear if the magnetite was intentionally added as there is no obvious functional benefit to its addition and fluxing has been ruled out (Pryce et al. 2010:256; cf. Bennett 1989:332). It is most likely that this iron ore came from the copper/ iron ore deposit at nearby Khao Tab Kwai and, for some reason, was purposely added to the smelt; Bennett (1989:334) records that some of the iron ore samples she analyzed from this deposit contained as much as 28% copper. While the crushed magnetite did not enhance the smelting process, it has been suggested that it might have been used as a cover

PREHISTORIC COPPER MINING AND SMELTING

over a crucible charge. Such a cover of crushed magnetite or slag would provide a “gas-trapping mineral blanket” that would facilitate the smelt by trapping hot smelting gases (Pryce et al. 2010:256; Rostoker et al. 1989). There is, however, currently no certain archaeological or analytical evidence as to why the iron ore was included.

Nil Kham Haeng Nil Kham Haeng (NKH) lies about 3 km to the south of Non Pa Wai and has ample evidence for human burials and habitation remains intermingled with massive ore processing, smelting, and casting. Four operations were excavated by TAP in 1986, 1990, and 1992, yielding a total of ca. 407 m3 from a site that is ca. 5 hectares, if not more, in size and more than 6  m deep at its maximum (e.g., Natapintu 1988, 1991; Pigott and Natapintu 1988; Pigott et al. 1997). As proposed in Rispoli et al. (2013), KWPV ceramic typology and a small number of 14C dates suggested that activity at the site commenced shortly after the mid-point of the 1st millennium B.C. with intensive copper production accelerating during the final centuries of the millennium and continuing into the early centuries of the 1st millennium A.D. However, as stated in the introduction to this chapter, preliminary indications from the new TAP AMS 14C dating program currently underway are suggesting that the Rispoli et al. (2013) chronology will have to be reconsidered, the suggestion being that Nil Kham Haeng may be several centuries earlier than thought. This adjustment would in turn indicate that production at Non Pa Wai and Nil Kham Haeng overlapped more than was previously thought (Table 2.2). The precise reasons for the establishment of another perhaps contemporaneous, copper production/habitation site at Nil Kham Haeng, so near to Non Pa Wai, remain unclear. Occupants of Nil Kham Haeng most probably were exploiting multiple small deposits located nearby, high on the adjacent mountain of Phu Kha, where indications of “old workings” (e.g., adits, galleries) are present. Although production at KWPV sites cannot at present be conclusively linked to specific local ore deposits, excavation notes show that at Nil Kham Haeng there was a greater proportion of sulfur-bearing

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(pyritic) copper ores and host rock encountered in its matrix than at Non Pa Wai, as documented by TAP geologists Udom Theethiparivatra and William W. Vernon. Exhaustion over time of surficial, oxidic copper ores in local deposits may have necessitated increasing exploitation of deeper-lying, copper sulfide deposits (Pryce et al. 2010:244); however, this may also simply be a factor of the composition of the sulfide orebody on Phu Kha. Unlike Non Pa Wai, Nil Kham Haeng clearly was a copper-producing settlement at which people lived, died, and were buried during the centuries of occupation. Living floors with numerous posthole patterns and burial cuts were excavated. Nil Kham Haeng domestic ceramics share common typological traditions with Non Pa Wai and other prehistoric sites in central Thailand (Rispoli et al. 2013). Habitation evidence at Nil Kham Haeng was mixed with the ore/slag crushing and production debris that comprise the site’s massive bulk. The site’s almost varve-like stratification of crushed debris is also found at Khok Din in the KSOMD (Rispoli et al. 2013:139). At Phu Lon I (Pottery Flat), a shallow deposit of similar crushed debris was found, but it did not exhibit the multitudinous, thin lenses seen at the above sites. The unusual stratigraphic matrix of Nil Kham Haeng reflects a distinct difference in the technological system of ore processing from that observed at Non Pa Wai. At the latter site, the Industrial Deposit was a thick stratum packed with debris in an ashy, powdery soil matrix, and there was no evidence for fine-grained, ore beneficiation. At Nil Kham Haeng, on the other hand, thin-lensed, multitudinous strata consist of layers of finely crushed (down to pea-size) ore, host rock and slag fragments (Color Fig. 2.27). The process of strata formation at Nil Kham Haeng appears to result, in part, from flattening on the site’s surface of the finely crushed gravel as a result of annual monsoonal rainfall and by human and animal foot traffic across the site. The sheer volume of crushed debris indicates that substantially more human effort was being devoted to ore processing at Nil Kham Haeng than at Non Pa Wai, and this difference may relate to the Nil Kham Haeng copper ores requiring, or at least undergoing, more beneficiation to separate ore from host rock. Nil Kham Haeng metalworkers chose to crush the ore quite finely, but not to a powder that would block airflow during smelting. Fine crushing facilitated

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the smelting process; in the smelting crucible a multitude of small ore fragments offered more exposed surface area to hot smelting gases; hence reduction could proceed more effectively. Mortuary deposits provided examples of both finished metal products and manufacturing equipment. The 14 burials that were excavated at Nil Kham Haeng contained metal artifacts and ceramics that closely resemble those found at sites in the KSOMD, ca. 28 km southeast of Nil Kham Haeng. At Nil Kham Haeng, one burial contained five carnelian beads, a complete but disassembled chimney, a bundle of copper-base cordiform artifacts, and long rows of bangles presumed at the time to be of iron and covering each forearm (Frontispiece; White and Pigott 1996:166, fig. 13.9; for copper-base examples see Rispoli et al. [2013:142, fig. 22]). These bracelets remain unanalyzed, but upon recent re-examination of excavation photos by the author, they appear to copper-base. Four of the 14 burials had copper-base finished products, including a tin bronze spear point in one burial and three other burials with bundles of the cordiform artifacts. In one of these latter burials, one splayed adze/axe head with a miscast (solid) socket was also of tin bronze. The two tin bronze artifacts at Nil Kham Haeng are thought to be imports, as excavators found no direct evidence of tin bronze manufacture at Nil Kham Haeng. Laboratory analysis of slag from the site did indicate trace levels of tin (Pryce et al. 2010:255, table 7). Apparently, tin was introduced at some point in the production cycle; Pryce suspects, but cannot demonstrate, that this occurred at one or more stages including, but not limited to, refining and recycling. Five burials each had a single, complete, and possibly disassembled chimney included among the grave goods. Three of four burials with cordiform artifacts also contained chimneys. One of these chimney burials included what has been interpreted as a possible crucible (Fiorella Rispoli, pers. comm.; see further discussion of crucibles in the KSOMD section below).

nil kham haeng: slag cakes Nil Kham Haeng slag cakes appear, from the excavated sample, to have been of a size smaller than those at Non Pa Wai, e.g., ca. 7–10 cm in diameter and up to 0.5 kg (see Pryce et al. 2010:251 and tables 3, 6). From early on, TAP researchers hypothesized that the Nil Kham Haeng slag cakes, as at Non Pa Wai, were being broken into smaller pieces, perhaps to be resmelted for their residual copper or to be used as a flux. However, the purpose for breaking up the slag cakes remains unclear (see Rostoker et al. 1989; cf. Pryce et al. 2010:251, 256). Such slag cakes had to have been formed from the post-smelting evacuation of Non Pa Wai type large smelting crucibles onto the site’s surface as described previously. Sherds of such crucibles were also excavated at Nil Kham Haeng, but in modest numbers as compared to the more abundant, yet enigmatic, “sherds” of highly friable chaff-tempered ceramic, discussed in more detail below.

nil kham haeng: slag casts A second category of slag artifact termed “slag casts” is known only from Nil Kham Haeng. These flat, circular disks were consistently 5–6 cm in diameter, about 1 cm thick, and with a weight between 50–100 g. They are relatively homogenous in composition as compared to Non Pa Wai slag, and perhaps were cast in a single, standard type of larger, shallow, thick-butted mold. Broken fragments of slag casts occurred with some frequency in excavation contexts and it has been suggested that the casts, often glassy in texture, are a product of the resmelting of slag cakes (Pryce et al. 2010:251). These purposefully cast disks were frequently broken into pie-shaped sections. Perhaps they were broken to determine if they held enough residual copper to merit resmelting. It is also possible that they represent the last remnants of the smelting crucible emptied out into waiting molds. The discarded slag casts also could be ingot pseudomorphs that contained no metal.

Smelting Byproducts

Smelting Equipment

Excavation at Nil Kham Haeng yielded vast amounts of slag, demonstrating on-site smelting activity. Two principle forms of the slag have been termed “slag cakes” and “slag casts.”

nil kham haeng: slag skins

During the excavations at Nil Kham Haeng, innumerable fragments of what were at the time termed “slag skins” were encountered in the site

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fill. These artifacts are slagged fragments of a friable, chaff-tempered ceramic fabric, and they were not found at Non Pa Wai. The core of each sherd is reduced and grey-black in color, as a result of its having been subjected to a prolonged reducing atmosphere. The sherd itself is held together by a skin of slag on its concave, interior surface. The friable exteriors of slag skins were generally unfinished as if that side of the ceramic had been applied while wet as a coating or lagging against, for example, the site’s loose, unstable gravel matrix. At excavation these artifacts were interpreted as possibly being the fragmented chaff-tempered clay lining (applied wet) of bowls dug into the site’s gravel surface to form roughly cylindrical “bowl furnaces” (Pigott et al. 1997:129). During the excavations, TAP researchers hypothesized that chimneys were placed around the lined bowls to create smelting installations. Frequently, roughly circular slag skins were found which looked as though they formed the bottom of the bowl. Once the smelting had stopped and had cooled it would have been easy to dig open the bowl furnace to obtain the cooled furnace contents, either a layer of slag resting atop a copper ingot in the furnace bottom or a fused mass of slag and copper prills. As demonstrated below, the above reconstruction is given additional credence based on finds of similar production remains at sites in the KSOMD. A second theory to explain the slag skins has been proposed, based on a reexamination by Pryce of the sample of Nil Kham Haeng slag skins on loan to the Penn Museum from the Thai Fine Arts Department. All examples had typical slagged interiors. However, in a few examples, the sherds also appeared to have finished exterior surfaces as one would expect from a crucible body sherd. Based on this evidence, Pryce suggested that the slag skin artifacts might be sherds of smelting crucibles (Pryce 2009: chapter 6; Pryce et al. 2010:247). The majority of the slag skin sherds examined lacked a finished exterior surface making the crucible explanation difficult to accept. In most instances, the exterior surfaces had spalled off. This spalling may be a post-depositional phenomenon. Slag skins may have weathered heavily over the centuries, losing much of their original surfaces, but also something in their composition or the manner of their manufacture may have contributed to their friability. It should be noted that Nil Kham Haeng slag skins are chemically the same as Non Pa Wai

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crucible sherds with the only differences existing at the trace element level (Pryce et al. 2010:248, table 6). Geologist/petrographer Janet Douglas (formerly of the Conservation Laboratory at the Freer/Sackler Galleries of Art at the Smithsonian Institution) has conducted thin-section analysis on both slag skins and crucible sherds, but the results remain unpublished. A third hypothesis as to the true function of the slag skins has been proposed and this is discussed in the section below devoted to the KSOMD. Ultimately, understanding how slag skins formed should reveal more specific information about the smelting activities taking place at Nil Kham Haeng; for the present, their origin remains unclear.

nil kham haeng: chimneys Nil Kham Haeng is distinguished not only by greater numbers of ceramic chimney sherds than Non Pa Wai, but also by the occurrence of complete but apparently disassembled examples of these in four burials (Frontispiece; see also White and Pigott 1996:162, fig. 13.5). Ciarla (2008:332) has argued that the chimneys were intentionally constructed so that they could be dismantled in order to make them portable. The chimneys at both sites are made of the same grit-tempered fabric and were also fired orange during repeated use. None were found in situ in functional contexts.

Metal Product Manufacture and Use There are indications that casting of finished products in addition to smelting occurred at Nil Kham Haeng. Although no amorphous fragments of casting spillage were identified during excavations at the site, bivalve molds occur with some frequency. While the full range of metal products manufactured at this site is still under study, the presence of small, copper-base socketed cordiform artifacts, and an example of a mold for these items, suggests that this artifact type may have been cast at the site. In prehistory, there clearly was notable interest in cordiform artifacts, which occurred in burials at Nil Kham Haeng, alone or in bundles often placed near the head (Frontispiece; Pigott et al. 1997:154, fig. 17, 155, figs. 18 and 19; White and Pigott 1996:166, fig. 13.9; see Color Fig. 2.28). There were close to 60 in one burial (Op. 2, Burial #3), one of four burials

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with such artifacts out of 14 burials excavated at the site (Pigott et al. 1997:130). From their presence in the four burials excavated in four 5 x 5 m operations in a site at least 5 hectares in size, it is clear that these artifacts were not only considered sufficiently available to be removed from circulation but also were deemed suitable for interment with the dead. Analyses of nine KWPV co-smelted, copper-base artifacts using several techniques (PIXE, electron microprobe, laser ablation quadrupole ICP-MS) indicate that they are made of unalloyed copper and contain considerable matte (copper-sulfide or copper iron-sulfide) inclusions, as well as several weight percent of iron (Bennett 1989:337–338; Pryce et al. 2011b:152, table 1, 154, table 3). These analyses also indicate that sulfur contained in the matte in these artifacts can run as high as 20 wt%. Such a composition could have resulted from the co-smelting of oxidic and sulfidic ores. It was originally thought that this matte-rich, high-sulfur copper might serve as a marker for a typical, known product of copper smelting at Nil Kham Haeng, in particular the cordiform artifacts. Sulfur is also present in the slag in variable amounts depending on the heterogeneity of the smelted copper ores and on sulfur’s volatility during smelting (Pryce et al. 2010:239, 253). A high level of sulfur correlates with a visually observed high rate (over Non Pa Wai) of pyritic minerals recovered during excavation at Nil Kham Haeng, as well as among samples that were analyzed (Pryce et al. 2010:244). Although sulfur-rich prills found in the slag are consistent with sulfur identified in the analysis of a few local metal artifacts (see Bennett 1989; Wang et al. 1994), the presence of sulfur cannot be seen as a marker of KWPV production due to its variable quantity (Pryce et al. 2010:253). The pliability of the cordiform artifacts (often the uncorroded copper in these artifacts can still be flexed) and their thinness (ca. 1–2 mm uncorroded), along with their frequently miscast shape, suggest that they were not used for tasks that required any kind of striking force. They may represent a copper ingot cast in a standard shape. Such ingots would be of recognizable KWPV provenance and were perhaps seen as a portable commodity of value, suitable for trade and exchange that, in the end, could be melted down, possibly for alloying with tin, and the metal then cast into implements and ornaments (Pigott et al. 1997:131; see also Pryce 2009:72;

Pryce et al. 2011b:151; Rispoli et al. 2013). These artifacts are among the thinnest, socketed metal artifacts known to have been produced by prehistoric Southeast Asian metalworkers. An interesting potentially analogous example of extremely thin, bundled copper-base artifacts in burials comes in the form of so-called naipes and/or axe monies from the central Andean region of Peru and Ecuador (Lechtman 2014:386–387; also Hosler et al. 1990). They occur in clusters in burials or hoards and were valued, in part, for their remarkable thinness, produced in this case by hammering. Some researchers have termed them “primitive money” and, at least in the Ecuadorian context, axe-monies “may have served in prehistory as tribute or as a medium of exchange” based on ethnohistoric and archaeological evidence (Lechtman 2014:387). Naipes in Peru, whose circulation was geographically circumscribed, may well have served as “a special form of wealth…an important status symbol, perhaps amassed in life for burial at death” (Lechtman 2014:387). At this juncture the true function of the KWPV cordiform artifacts remains open to question, but these Andean examples do offer some potential options for consideration. A unique ceramic mold half of a bivalve mold for the casting of “miniature” cordiform artifacts was excavated from site fill at Nil Kham Haeng. This mold was for the sequential casting of four of the smallest versions of what appear to be unsocketed cordiform artifacts (see Pigott 1999:19, fig. 17). Such artifacts were simply too small for the casting of a socket, while larger cordiform examples were socketed. It bears mentioning that at least one open mold for a small, unsocketed cordiform artifact was found at neighboring Non Mak La (Pigott 1999:18, fig. 13), and at least one bivalve mold fragment for a socketed cordiform artifact came from Non Pa Wai (Pigott 1999:17, fig. 12, top left). The presence of this shape at all three TAP sites in the KWPV indicates a shared typological similarity across time and space. Cup and conical ingot molds were found at Nil Kham Haeng, but in greatly reduced numbers compared to Non Pa Wai.

evidence for possible consumers of kwpv products A few examples of artifacts possibly related to the KWPV product line have been recovered in

PREHISTORIC COPPER MINING AND SMELTING

Thailand and elsewhere in Southeast Asia. Products similar to the cordiform artifacts have been identified during surveys and from excavations at other sites in central Thailand, including Tha Kae (Rispoli et al. 2013:139) and Noen Din in the KSOMD (Ciarla 2008:328, fig. 20). One was also found at the site of Ban Tham Tao, ca. 60 km north of the KWPV (Surapol Natapintu, pers. comm.), and a tin bronze version was found at the site of North Sa Kaew, about 55  km from the KWPV (Eyre 2006:301). Surface finds of similar artifacts have been retrieved in other sites in the Nakhon Sawan Province in the vicinity of Ban Phu Wisat and Ban Phu Wa villages (Fine Arts Department 1988:182, 189). At Nong Nor, southeast of Bangkok, eight small, thin socketed copper artifacts with Y-shaped blades were excavated from Burial 102. The Nong Nor cemetery was originally dated ca. 1100–700 B.C. and thought to be bronze period (Higham and Hogg 1998:25; see other dating in Higham [2002:147]; Higham et al. [2011a: 261]). The actual dating, based on stratigraphic, ceramic, and other associations, could be later, ca. 5th through 4th centuries B.C. (Fiorella Rispoli, pers. comm.; see also discussion of Nong Nor in Chapters 4 and 5). This would make them contemporary with other 1st millennium B.C. small-socketed cast artifacts, including the copper cordiform artifacts from the KWPV. The Nong Nor artifacts appear heavily corroded, but also there looks to be evidence of miscasting present in the form of porosity where the molten metal did not fully penetrate when flowing inside the bivalve molds. Such miscasting porosity is characteristic of cordiform artifacts recovered from Nil Kham Haeng. A proper comparison of the Nong Nor artifacts and KWPV molds, if combined with elemental and LIA of the copper-base artifacts, could facilitate a clearer understanding of the possibility of connections between Nong Nor and the KWPV. Significantly, in the southwest corner of northeast Thailand near Phimai in the upper Mun Valley, two copper-base cordiform artifacts were excavated in phase IA1 Burial 482 at Ban Non Wat (Higham and Kijngam 2012b:24, 25, fig. 2:19; see also Higham and Rispoli 2014:20, fig. 13). These two artifacts are typologically similar to those of the KWPV, best known from burials at Nil Kham Haeng. An electron microprobe elemental analysis (EMPA) on one of these two artifacts (SEALIP/TH/BNW11)

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indicates that it contains 6.5 wt% tin and 23.7 wt% lead (Pryce 2014:284, table 2). The tin and lead content of the Ban Non Wat cordiform artifacts would argue that they were alloyed and cast outside of the KWPV, although the casters used local molds designed to make artifacts similar to those used in the KWPV. The source for this artifact’s isotopic signature is as yet unidentified (T. O. Pryce, pers. comm. 2014). Interestingly, the Ban Non Wat cordiforms appear to be miscasts, an attribute commonly found in Nil Kham Haeng cordiforms. In summary, morphologically the Ban Non Wat cordiform artifacts resemble castings typical of Nil Kham Haeng, but both elemental and isotopic analyses argue that the raw materials came from outside of the KWPV, and they were likely cast outside of the valley as well. On the other hand, three other Ban Non Wat phase BA2 copper-base artifacts, (ca. 1000–900 B.C., dating reported in Higham and Higham [2009b:137]), namely two so-called axes and a chisel, have been linked by LIA to copper from KWPV deposits (Pryce 2012b:490–492; Pryce et al. 2011a:3320). The “axes” resemble some sort of tilling or digging tool such as a hoe or spade, rather than an axe. The BA2 “axe” SEALIP/BNW5 is by EMPA analysis a tin bronze with ca. 3 wt% tin, while artifacts BNW7 and BNW8 were too corroded for elemental analysis. The above LIA and EMPA results from phase BA2 provide evidence in support of the movement of KWPV copper to southern northeast Thailand where, perhaps, the copper was alloyed with tin imported from another area and cast into final products. Thus, the LIA evidence for KWPV copper at Ban Non Wat during its bronze period, and the presence of cordiform artifacts in Ban Non Wat during its iron period suggest that interaction of various kinds occurred between KWPV and the Upper Mun regions over time (see Higham and Rispoli 2014). Further afield, cordiform-like artifacts are seen to occur well outside the KWPV. In the PRC, cordiform-like artifacts, virtual twins to those found at Nil Kham Haeng, were found at Hejiashan (Dali, Yunnan, PRC) (Ciarla 2007a: 321, figs. 17A, B; Zhang 2000). The Hejiashan finds are bracketed between the end of the Spring and Autumn Period and the Middle Warring States Period, from ca. the end of the 6th to the 4th century B.C. However, the “goat horn” motif found on one of the cordiforms,

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and known elsewhere in Yunnan, is dated to ca. 3rd century B.C. A similar motif was found on a cordiform artifact from a Nil Kham Haeng burial. The Hejiashan cordiforms occurred among a group of 44 copper-base artifacts comprised mostly of “different types of small, almost miniature socketed axes” described as axes of yue type II (Ciarla 2007a:320– 321; see also Higham et al. 2011a:260). They were found during construction in an isolated pit, a cache perhaps, lined with marble slates. Their occurrence suggests yet another potential relationship between central Thailand and sites to the north that lie within the boundaries of the PRC. Though purely speculative, other possible typologically similar cordiform artifacts may be found on the island of Bali (Soejono 1972: plate 18, lower left). Cordiform artifacts, if they are related in some way, may either have been moving along networks of trade and exchange, or the shape was being copied by metalworkers in distant regions. Both options reinforce their attribution as a type of ingot. SEALIP conducted LIA on cordiform artifacts in Bali and results indicate no isotopic compatibility with ore sources in the KWPV of central Thailand (Pryce et al. 2018a). There is also evidence that suggests tin bronze artifacts were imported into the KWPV. Two Nil Kham Haeng tin bronze artifacts—the socketed spear point, which shares typological affinities with those known from Vietnam (Rispoli et al. 2013:123, fig. 13, nos. 4–5, 140), and the large, heavy, miscast adze/axe (Pigott et al. 1997:154, fig. 17, 157, figs. 23, 24)—may well be imports given their anomalous shapes for the KWPV. Lead isotope analyses would help to confirm such an inference.

KWPV: Production Process Overview Differences between Non Pa Wai and Nil Kham Haeng are apparent in site formation processes, in smelting parameters, and in slag chemistry. The basic chaîne opératoire of Non Pa Wai metalworkers was used for centuries and shows little evidence of change over the life of the site. Copper production at nearby Nil Kham Haeng, which now appears to have occurred simultaneously as Non Pa Wai production was generating its massive Industrial Deposit (Table 2.2), ultimately was of a comparable, if not larger, scale and involved considerably more human effort.

If the source of copper smelted at Nil Kham Haeng was nearby Phu Kha, the ore must have been carried on the backs of miners, as the mine area is too steep and rugged to use pack animals if they were in use at the time. Constant ore and slag crushing down to pea-sized gravel at Nil Kham Haeng signaled a variation in how copper ores were being processed in the KWPV. At Non Pa Wai, ores were being crushed for smelting, but not with the intensity exhibited at Nil Kham Haeng (see Pryce et al. 2010:256–257). These innumerable days, months, and years of human effort resulted in surface piles that formed perhaps around anvils during crushing, and which were flattened under foot and compacted during monsoons, leaving the finely lensed, unique stratigraphy found at Nil Kham Haeng. These layers were interleaved with living surfaces, human burials, domestic potsherds, and animal bones, all markers of village life. At Nil Kham Haeng, prehistoric people were living, smelting, and being buried on the site, in contrast to Non Pa Wai, where no burials were encountered in the Industrial Deposit, i.e., above the site’s basal deposit. The smelting paraphernalia at Nil Kham Haeng is related to that of Non Pa Wai, as indicated by the presence of smelting crucibles and chimneys. Subtle differences in the smelting process and copper-base metal produced at each site may relate to the choice and variability of copper ores available to metalworkers at each site. Laboratory analyses of slag indicate that a consistently more efficient extraction process was achieved at Nil Kham Haeng, in part, through better formulation of smelting charges and a greater ability to generate higher smelting temperatures (Pryce et al. 2010:256–258). “A more effective generation and distribution of heat (perhaps through refinements in forced draught delivery) may have been an important factor in the improving trend in copper production in the later prehistoric Valley” (Pryce et al. 2010:256). This, in turn, meant a more efficient capture of copper during the smelting process such that the overall copper losses evident in slag were both reduced and stabilized over time (Pryce et al. 2010:251). Nil Kham Haeng metalworkers appear to have practiced deliberate co-smelting, again with the addition of the enigmatic iron oxide fragments (Pryce 2009; Pryce et al. 2010:261). The presence of the unreacted iron oxide at both Non Pa Wai and Nil Kham Haeng is an important technological link

PREHISTORIC COPPER MINING AND SMELTING

between the two sites and can be interpreted as additional evidence of technological continuity across the KWPV, though the purpose of the iron oxide remains unknown (Pryce et al. 2010:264). Continuity too is seen in the consistent slag microstructure at the two sites, with the main difference being a greater abundance of residual minerals in Non Pa Wai slag (Pryce et al. 2010:251). TAP research in the KWPV has long sought clues to the air delivery mechanism for smelting. During the excavations it was thought that smelting was wind driven, taking advantage of the strong prevailing winds during the dry season. (For an Aegean example of wind-driven copper smelting in a perforated furnace, see Catapotis et al. [2008].) In Pryce’s estimation, smelting by wind is not thought to have been feasible using the KWPV paraphernalia (Pryce et al. 2010:249, 261). The only possible archaeological remains that might relate to air delivery are the so-called furnace chimneys, best described as perforated ceramic cylinders. Pryce’s replication experiments led him to conclude that they were not part of the smelting process. He suggested instead that they may have a role in the foundry (melting and casting) process (Pryce 2009: chapter 7; Pryce et al. 2010:247–249). Nonetheless, as is seen below, Ciarla (2008:330–336) argued for a smelting-related role for the chimneys, based on LoRAP excavations in the KSOMD and on how the chimney was arranged in relation to the charge. As at Nil Kham Haeng, a large number of chimney sherds were excavated in site fill in metallurgical activity areas at Khok Din and at Noen Din as well as the remains of a complete chimney in one Noen Din burial (Ciarla 2008). At this juncture, just how smelting at TAP sites was driven remains unclear. A better ability to maintain a higher smelting temperature and to manipulate charges for reduced metal loss are two key technological developments essential to the more efficient smelts in evidence at Nil Kham Haeng (Pryce et al. 2010:256–258). This variant technological system resulted in less copper being lost in the slag (Pryce et al. 2010:259, 262). Production at Nil Kham Haeng was marked by intensification as evident in the ore/slag crushing, by a more efficient and standardized smelting process, apparent, in part, in the homogeneity of production debris across the vast expanse of the site. Pryce and colleagues (2010:259) state that this improved

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extraction “efficiency probably came at the cost of a much increased labour input.” The enormous bulk of the site, built up over the course of several centuries, suggests that massive amounts of human time and effort went into the manual act of ore and slag crushing followed by sorting of the ores for smelting. This intensification is consistent with a substantially increased demand for copper-base metal (e.g., tin bronze in northeast Thailand) in the later centuries of the 1st millennium B.C. and perhaps even into the early 1st millennium A.D. (Pryce et al. 2010:237, 259; also Higham and Higham 2009b). Such an assertion requires evidence that some of the tin bronze excavated at northeast Thai sites was sourced from the KWPV. The possibility exists that KWPV copper was being used in the manufacture of tin bronze in northeast Thailand during that region’s bronze period, as the LIA evidence from Ban Non Wat outlined above indicates. Arguments presented by Higham and Rispoli (2014) demonstrate a strong connection between the KWPV/Lopburi region and that of bronze-using settlements of the upper Mun Valley of southern northeast Thailand during the 1st millennium B.C. Trade and/or exchange in KWPV copper eastwards onto the Khorat Plateau and its sites is certainly within the realm of possibility. Given the difficulty of mining, smelting, and casting metal during the wet and humid monsoon season, primary metal production was probably a dry season activity in the KWPV and elsewhere in prehistoric Thailand (White and Pigott 1996; see examples of Southeast Asian seasonal metal production in Bronson and Charoenwongsa [1986]). At Non Pa Wai and Nil Kham Haeng, in the contexts that span the 1st millennium B.C., no well-defined workshops or areas of clearly differentiated metallurgical activity were identifiable. At both sites, the massive quantities of production remains were homogeneously distributed across several hectares. The lack of specialized activity areas and the many similarities of the technological systems practiced within these massive sites over considerable time suggest that the work was done by groups of workers operating independently rather than under some form of central control. The groups involved might have been kin-based as they must have worked next to one another for days, months, and years in “a community-based mode of production” (White and Pigott 1996). Shared technological traditions would

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be more characteristic of culturally related groups than of culturally disparate groups working in proximity to one another at the same location to exploit a common resource. On the other hand, although Nil Kham Haeng and Non Pa Wai share some similar artifact types (e.g., cordiform artifacts, small bivalve molds, cup and conical molds, crucibles, chimneys), differences in the presence and prevalence of such productionrelated artifacts at the two sites as well as differences in the smelting procedures, suggest that these sites may have had distinctly different communities of practice, while at the same time sharing common underlying cultural and technological traditions upon which their copper production activities were based. The existence of similarities and differences in the metallurgical evidence among the KWPV sites strongly indicates that “community of practice” models would help to explain how technological traditions were shared among the distinct communities at the two production sites that temporally overlap (Table 2.2; see TAM 2A, chapter 4, and Chapters 5 and 6 in this volume for more discussion of communities of practice). The differences between Non Pa Wai’s Industrial Deposit and Nil Kham Haeng’s production evidence—e.g., crucible smelting and massive quantities of ingot casting at Non Pa Wai versus probable crucible-based bowl furnace smelting and massive beneficiation at Nil Kham Haeng—suggest that there may have existed more than one community employing distinct but related technological systems over time.

Non Mak La Roughly 500 m south of Non Pa Wai lies Non Mak La, a prehistoric occupation and burial site with some smelting evidence, with chronological and cultural links to Non Pa Wai and Nil Kham Haeng (Pigott et al. 1997:133–134; Weiss 1989). The site is marked by a shallow surface artifact scatter spread over more than 70 hectares along the south bank of the Huai Pong watercourse, which forms the site’s northern edge. This artifact scatter is the result of constant plowing of rich soils along the Huai Pong’s south bank that has blurred the periphery of the prehistoric cultural deposit (see surface survey maps in Weiss [1989]). As a result, the original extent of

the site is not known. The four trenches excavated in 1985 by CTAP under Surapol Natapintu’s direction uncovered evidence of major metalworking as well as some habitation (Bennett 1988a; Natapintu 1988:116, 119). The CTAP excavation was followed in 1994 by a TAP excavation in a distinct area of the site along the Huai Pong; 257  m3 were excavated from seven 5 x 5  m operations in which cultural deposits reached at least ca. 2  m deep. Dr. Judy C. Voelker at Northern Kentucky University is analyzing the results of the TAP excavations at Non Mak La. Results of the CTAP excavations are discussed below, following the discussion of the more recent TAP fieldwork.

Non Mak La: 1994 TAP Excavations Occupation at this multi-period site, though not continuous, is thought to span from the early 2nd millennium B.C. to the later 1st millennium B.C., based on a small number of unpublished radiocarbon dates and typological ceramic links to other sites in central and northeast Thailand. The area TAP excavated in 1994 shows that this region of Non Mak La was used for habitation and burial. Habitation is evidenced by living surfaces, domestic ceramics, and faunal remains. Burials were found across most of the excavated area; 56 primary burials were identified, some of which were young children buried in pots. The excavated area yielded very few metal artifacts and only a modest amount of debris from the production of metal. At least six copper-base metal final products were excavated at Non Mak La—four bracelets in one burial, a ring in another, and a thin, flat non-socketed adze/axe with a splayed blade in the fill. Amorphous fragments of copper casting spillage were not identified during excavations at Non Mak La, or at any TAP site in the KWPV for that matter. Why this is the case given that casting was being conducted at these sites with some frequency remains unclear.

metal production evidence at non mak la from the 1994 excavations The remains of copper metalworking activity in the excavated area were modest especially when compared to that from Non Pa Wai and Nil Kham Haeng, but included enough items to link Non Mak

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La to these two neighboring sites. Material included slag, large crucible sherds, cup/conical and bivalve molds, and chimney sherds. These were all found scattered in the excavated site matrix. Of particular interest are two possible copper ingots excavated in the site fill, not associated with any particular feature (see Fig. 2.26; also Pigott 1999:18, fig. 15). They were probably cast in a small cup mold of a Non Pa Wai type. These are the only probable examples of such ingots excavated from the KWPV, but two similar finds were recovered from later 1st millennium B.C. levels at Tha Kae (Rispoli et al. 2013:136). Among the molds identified at Non Mak La was one for a very small, flat (unsocketed) cordiformshaped artifact carved into a discarded, large adze/ axe mold fragment of the type known from two founder’s burials in basal Non Pa Wai, which in turn provide some of the earliest evidence of metallurgical activity in the KWPV (Pigott 1999:18, fig. 13). Cordiform artifact molds are thought possibly to have been used in the casting of a type of ingot characteristic of copper production at KWPV sites, and, as such, these molds may represent a particular technological link between Non Mak La, Non Pa Wai, and Nil Kham Haeng. The area of Non Mak La excavated in 1994 is of particular interest because it provides distinctly different taphonomic and activity evidence from that found at Non Pa Wai and Nil Kham Haeng at a time when artifact typologies and dates suggest that occupations at the three sites were to some degree contemporaneous. The other two KWPV sites have massive evidence for copper smelting; the TAP excavated area of Non Mak La yielded some production remains, but not on such a large scale. Non Mak La has evidence of habitation, as does Nil Kham Haeng, but at Non Pa Wai only domestic ceramics and faunal remains suggest habitation, with no identifiable postholes or living surfaces in evidence in the Industrial Deposit. Non Mak La has a large number of burials (56 primary), while on the Non Pa Wai Main Mound only 18 were identified (all found within the basal deposit), and only 14 burials were found at Nil Kham Haeng. Such figures are, of course, biased in part by the amount of excavation undertaken at each site as well as by apparent differences in site function. Given the massive size of the two main production sites, they yielded only modest numbers of actual copper-base finished products, although Nil Kham

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Haeng yielded the most, primarily from burials. Non Mak La is the only TAP site from which possible cup mold-cast ingots were excavated. The three sites are geographically close, and given their shared material culture, they were clearly linked in certain periods (see Fig. 2.14). Continuing study of excavated materials from all these sites will shed further light on their interrelationships.

non mak la: 1985 central thailand archaeological project excavations Although little metal was recovered during the 1994 TAP excavations at Non Mak La, in 1985 significant metallurgical production activity was documented elsewhere on the site by CTAP. Natapintu and his team excavated three test trenches in an industrial area and one trench in a domestic habitation area (Natapintu 1988:116, 119). These excavations were not in proximity to the 1994 TAP excavations so the chronological correlation between the CTAP and TAP excavations is not clear. Excavation of the industrial area identified what Natapintu describes as “a large glassy slag heap about 1 meter deep and more than 100 square meters in area” (Natapintu 1988:119). Two of the test trenches in the slag heap yielded some 3500 kg of slag from a total surface area of 4 x 5 m, an exceedingly dense concentration of slag (Bennett 1988a:129). The slag heap yielded a single cordiform-like, but unsocketed, copper artifact (Bennett 1988a:133, fig. 10, 1989:337, plate 5), slag cakes (Bennett 1988a:129, fig. 2, 1989:340, Plate 8), crucible sherds, tuyeres, fragments of furnace lining, and the ores of copper and those of iron (hematite, magnetite) possibly from nearby Khao Tab Kwai (Bennett 1989:332–334; Natapintu 1988:118, fig. 10). If ore beneficiation was taking place at this locus, this was not mentioned by the excavators. The numerous crucible sherds excavated appear to resemble those known from Non Pa Wai (see description in Bennett 1989:343–344). It is also possible that ceramic chimney sherds were found in this 1985 excavation at Non Mak La, although the reports are not clear (Bennett 1989:344). Interestingly, a human skeleton was uncovered in the slag heap, with a piece of what was termed iron slag in the pelvic region (Bennett 1988a:130). As at Non Pa Wai and Nil Kham Haeng, the slag from the heap appears to consist of intact and/or

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broken slag cakes with flow patterns suggesting that they had been poured from the smelting crucibles onto the ground. These cakes had soil impressions on their bottom surfaces (Bennett 1988a:129, 1989:338–339). The largest cakes weighed over 1.2 kg with diameters greater than 15.5 cm and as thick as 5.5 cm. Many cakes had been broken up after cooling, perhaps to check for residual copper. Bennett (1988a:129) stated, however, that in most cases the copper is microscopically disseminated and is of a quantity that would make recharging into a future smelt uneconomical (cf. Pryce et al. 2010:257 and table 7; see also Bennett [1989:339–343] for a comparative analysis of Non Mak La and Non Pa Wai slag). Bennett reported the presence of arsenic in the micro-prills trapped in the slag at levels up to 5.5% and has stated that this would have had a hardening effect on copper metal produced (Bennett 1988a:129, 134, 1989:337). The arsenic could have come from local ores, incompletely weathered copper sulfide orebodies that had devolved into oxides, carbonates, and silicates in the upper reaches and deeper-lying sulfides. However, neither Vernon’s KWPV geological survey nor Pryce’s analysis of KWPV smelting products noted the presence of arsenic. Bennett found no evidence for ore roasting, a process that would have volatilized both the arsenic and sulfur present. However, the amounts of sulfur present would not have impeded the smelting especially if fed into a co-smelting process (Bennett 1988a:129–130). From Bennett’s (1989:338–339) descriptions, the above-mentioned slag cakes from Non Mak La, with the exception of the arsenic, are quite similar to those excavated at Non Pa Wai and Nil Kham Haeng. This observation suggests a common crucible smelting tradition among these KWPV sites. The copper artifact CTAP excavated from the Non Mak La slag heap is described by Bennett as an unfinished and miscast arrowhead, though it is not pointed. It was clearly cast in a bivalve mold, as what may be its casting sprue is still attached to the artifact’s tang (no socket is present), and there is a casting flash along the outer edge of the body of the artifact (see Bennett 1989:346, fig. 10). This artifact was made of copper with up to 0.8 wt% arsenic and 1–4 wt% iron with an inhomogeneous composition (Bennett 1989:337 and table 5). The shape,

size, and thickness are reminiscent of the unalloyed cordiform, but socketed, artifacts known from Nil Kham Haeng. The iron minerals recovered at Non Mak La, hematite and magnetite, most probably came from nearby Khao Tab Kwai, the large iron deposit known to have copper minerals present as well. Pryce’s analyses of Non Pa Wai and Nil Kham Haeng slag documented the occurrence of unreacted fragments of the iron oxide ore magnetite trapped in the slag (Pryce et al. 2010:256, 258, fig. 11). Bennett (1989:334) noted that some samples of iron ore from Khao Tab Kwai had copper minerals “deposited within the fissures in the dense iron oxide,” with her analyses indicating as much as 28% copper present. Such copper-rich iron ores could have been smelted to copper, and Bennett suggested such ores “could have been partially self-fluxing” (Bennett 1989:334). However, Pryce discounted iron oxide’s role as a fluxing agent in copper smelting as it was clearly not serving this function thermodynamically. At present, as discussed above for the other KWPV sites, it is not clear what function the purposeful addition of this iron mineral served. There is nothing in the evidence from the 1985 CTAP excavations that suggests that copper smelting was conducted in any way other than with the techniques identified for Non Pa Wai and Nil Kham Haeng. The procedures likely involved crucible-based copper smelting that yielded slag cakes as residue, a technological commonality characteristic of prehistoric copper smelting in the KWPV. Copper was being cast in bivalve molds, including artifacts in the cordiform tradition. There is no mention of cup or conical molds from the Non Mak La slag heap. For a more detailed account of Bennett’s study of Non Mak La metallurgy and that of additional related KWPV sites, see Bennett (1988b). Natapintu (1988:119) mentioned the occurrence of “furnace lining/wall fragments” and tuyeres from these excavations, and it is likely these artifacts derive from historic period ironworking rather than prehistoric copper working. This is, however, pure speculation at this point. There is no copper smelting system as yet known from prehistoric Southeast Asia that used tuyeres, and there is no evidence of built furnaces being used in KWPV copper smelting. Also, Bennett (1988a:130–131) stated that a small percentage of the Non Mak La slag she analyzed came from iron

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smelting, but that there was no evidence by which to date this activity (see below). Ores of both copper and iron were identified as present in these excavations by geologist Udom Theethiparivatra. Natapintu (1988:119) felt that the Non Mak La slag heap dated to somewhere in the 1st millennium B.C., and it appears that both copper and iron smelting occurred in the same context, but it is unclear if the iron smelting evidence is contemporaneous with the prehistoric copper smelting evidence here. Furthermore, it should be noted that the intensive surface survey at Non Mak La conducted for TAP by Weiss (1989) yielded surface evidence of ironworking in the form of tuyeres, plano-convex smithing hearth buns (PCBs), and furnace wall fragments. The latter consist of hammerscale and slag that fused together in the smith’s hearth in which iron blooms and/or iron artifacts were repeatedly heated and hammered to shape. Such buns and tuyeres also were excavated at the start of the TAP 1994 Non Mak La season in a probable later historic period ironworking context that was very close to the surface.

Metallurgical Activity in the KSOMD In 1989, the LoRAP team identified an archaeological area near a limestone outcrop known as Khao Sai On (“Soft Mountain”) located about 28 km southeast of the main KWPV smelting sites. This area is now known as the Khao Sai On Mineral District, Ban Nikhom 3, Amphoe Muang, Lopburi Province (Ciarla 2007b:396, fig. 1, 2008:314, fig. 1; see also Fig. 2.14). LoRAP conducted surface reconnaissance and excavation in the KSOMD intermittently during 1988–1992 and 2006–2008. Most recently a high intensity, systematic site survey in this area was undertaken by Pryce and colleagues (2013) that added a number of small sites, some metallurgical, to the local inventory. Also in 1989, Mauro Cremaschi in a LoRAP-sponsored geomorphological survey noted veins of copper ore in the Khao Sai On limestone outcrop (Cremaschi et al. 1992:168, fig. 1; see also Ciarla 2007b:397, fig. 2). Here, the team identified one small copper outcrop with an open pit mine and adit (Ciarla 2007b:398–400 and fig. 5). Survey around the outcrop in a ca. 2 km radius identified several metallurgical sites including

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those discussed herein, Khok Din and Noen Din (Ciarla 2007b:396–400). Fieldwork at these sites revealed evidence for copper production that closely resembles that from Nil Kham Haeng in the KWPV. Khao Sai On is a contemporaneous, small-scale smelting locality that mirrors the massive production occurring to the north (see Table 2.3). Though speculative at this point, one could suggest that mining and smelting in the KSOMD developed as a satellite industrial area, linked to Nil Kham Haeng, but exploiting more distant local ore deposits in response to the burgeoning demand for copper over the course of the 1st millennium B.C. and into the early centuries of the 1st millennium A.D.

Mining at Khao Sai On An open-pit mine is located on the eastern slope of the small monadnock of Khao Sai On and is thought to be later 1st millennium B.C. in date. At a higher elevation on this hill, further mining activity is suspected and includes at least one adit and shaft. According to the excavators, this latter activity may date to the middle/late bronze period (Ciarla 2007b:399–400), but at present there is no effective means to directly date such mining activity.

Copper Production at Khok Din The site of Khok Din is located ca. 88 m from the Khao Sai On outcrop where the open-pit mine was surveyed. Khok Din is composed of ca. 500 m2 of copper smelting debris. The deposit is comprised mainly of numerous lensed layers of finely crushed ore and host rock (e.g., quartz and diorite with copper oxide residues) that may have been extracted from the nearby open-pit. The deposit also contains significant amounts of finely crushed smelting slag as well as the hammerstones and anvils used in crushing, evidence of beneficiation that is very similar to that at Nil Kham Haeng. In terms of ceramic artifacts, there are crucible sherds, chimney sherds, and slag skins intermingled with domestic potsherds, the latter suggesting some level of habitation-related activity. The repertoire of metallurgical artifacts from Khok Din and nearby Noen Din compares to that from Nil Kham Haeng. Currently, the KSOMD sites are broadly positioned by the excavators between ca. 200 B.C. and

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A.D. 200 (Ciarla 2007b:398–399; see also Rispoli et al. 2013:109, fig. 4; and Table 2.2 [this chapter] to view the current relative position of the KSOMD chronology). As the KWPV chronology comes under revision, just how the KSOMD sites would compare remains a subject for future discussion.

Copper Production at Noen Din About 1.5  km northeast of Khao Sai On lies the site of Noen Din (“Earth Clearing”). The Noen Din metallurgical site is ca. 50 x 60 m in size (Ciarla 2008:315–316, figs. 2, 3). The excavated deposit, ca. 150  m2 in total, was in places ca. 70–110 cm thick and contained finely crushed, very small fragments of copper-bearing host rock, again evidence of beneficiation similar to Nil Kham Haeng. This host rock has been described as skarn with traces of chrysocolla, azurite, malachite, and crushed slag of minute size (Ciarla 2008:315, 316, fig. 4). Noen Din’s matrix was replete with the artifacts of copper production: crucible sherds, chimney sherds, bivalve molds, slag, and slag skins. The excavators observed that the Noen Din deposit accumulated as a result of “repeated dumping of waste from metallurgical activities carried out nearby or beneath a few scattered houses” (Ciarla 2008:329). The presence of houses is suggested by a smattering of postholes. A total of six burials were found, five adults and one infant. The burials may have been placed underneath the houses (cf. White and Eyre 2011). At Noen Din, in the locus known as “The Northern Trenches,” a single layer in Operation 2 was filled with production-related artifacts including crucible, chimney, and mold fragments, as well as hammerstones and anvil stones. These artifacts were found together with a large pile of calcium carbonate boulders (bedrock) that appear to have been intentionally broken. This area was located on the edge of the settlement and has been interpreted as a specialized locality for copper smelting (Ciarla 2008:321). These boulders (from the caliche substrate of the region), it is suggested, may have been crushed at this location and the fragments added to the smelting process as a flux (Ciarla 2008:322). Operation 1 at Noen Din yielded four of the site’s six total burials, attributed to two mortuary phases, echoing the presence of burials in a copper smelting context as seen at Nil Kham Haeng.

Three of the burials, two adults in Operation 1 (G1 and G2) and one infant (G6) in Operation 5, had metallurgy-related grave goods. In Operation 1, the upper and more recent phase contained ceramic crucible sherds at the top and then, somewhat deeper, was one of the burials (G2). This burial contained a single pot, fragments of copper-base metal bracelets, two carnelian beads, a glass bead in imitation of carnelian, and a disassembled ceramic chimney (Ciarla 2007b:400–401, 2008:333, fig. 28). This Noen Din burial parallels those from Nil Kham Haeng, where chimneys were found in four of the 14 burials excavated there. In one of the Nil Kham Haeng burials that contained chimney fragments, five globular carnelian beads also were found (Frontispiece; White and Pigott 1996:166, fig. 13.9). The presence of carnelian beads is suggestive of a date in the second half of the 1st millennium B.C. (Rispoli et al. 2013; see also Theunissen et al. 2000). In Operation 5, the burial (G6) of a newborn infant is of particular interest because of its elaborate personal ornaments as well as the inclusion of ceramic bivalve mold halves as grave goods. Ornaments consisted of a necklace of eighteen globular carnelian beads and one barrel-shaped bead, plus a shell anklet (broken, but in situ) with five barrel-shaped shell beads. Three ceramic pots also were present in the burial, as well as a cluster of nine ceramic bivalve molds. Each mold valve was different from the others in terms of the shape and the size of the profile of the casting impression (Ciarla 2008:326, figs. 15– 17). One mold was for an adze/axe, while another was a mold reminiscent of those for cordiform artifacts excavated at Noen Din in a burial (G1, see Ciarla [2008:328, fig. 20]) and in multiple quantities at Nil Kham Haeng. Interestingly, some of the grave goods had been repaired or were no longer usable. The molds, for example, appeared “exhausted” and some were broken. Such items are thought to be of “symbolic memory” in the burial, but of little further practical use (Ciarla 2008:327).

KSOMD: Production Process Much detail on copper production activities has come from the study of the chimneys from the Khao Sai On sites. The chimneys had an average external diameter of ca. 30 cm with walls ca. 6–8 cm thick (Ciarla 2008:331, fig. 26). This would leave

PREHISTORIC COPPER MINING AND SMELTING

an interior diameter of ca. 14 to 18 cm. At the midpoint of the chimney wall are four or five holes ca. 3.5–4.5 cm in diameter. Along the bottom edge of the wall, three arch-shaped openings are set at regular intervals. The chimneys are built up with coils of grit-tempered clay (at least two for the body, one for the rim). The clay is tempered with calcite fragments, also noted in ceramic bivalve molds at the site. The calcite may offer improved refractory properties, but it is not clear if it had been added intentionally (Ciarla 2008:332). After shaping, the chimneys were “probably cut while still wet into three or four gently curving slabs which when dried and fired, might be assembled or disassembled.” (Ciarla 2008:332). Disassembled chimneys may have been purposely designed for portability. Chimneys excavated in Noen Din (Ciarla 2008:333, fig. 28) as in Nil Kham Haeng burials, were complete, but disassembled. These could have been placed in a burial in an intentionally disassembled state, rather than having been crushed in place over time (e.g., Pigott et al. 1997:155, figs. 17 and 18; White and Pigott 1996:166, fig. 13.9). At both of these sites the chimney slabs were identically positioned at one end of the grave cut, along its outer walls. Finally, ceramic biconical plugs excavated from site fill at Noen Din have been interpreted as “windstoppers,” which could have been used to control wind and/or the bellows blast as well as the hot gases flowing through the chimney perforations by selectively inserting them in the perforations in the chimneys (see Ciarla 2008:332–334, fig. 29). These artifacts are unique to sites in the KSOMD. At the Khao Sai On sites, the excavators pointed out that crucible sherds (no intact example of a crucible was found) occur with less frequency than slag skins, chimney fragments, and crushed host rock, ore, and probably slag. This was also true at Nil Kham Haeng. (See earlier discussion of slag skins at this site.) Slag skins are described as “rim and wall fragments of what seem to be rather crude, bowlshaped ceramic containers whose internal surface is coated by slag, while the outer surface appears to [be] severely scraped off or completely lacking” (Ciarla 2008:334). In using the term “containers,” Ciarla was not referring to free-standing intact ceramic vessels, but rather bowl-shaped depressions (ca. 20–25 cm in diameter), which had been lined with a wet, chaff-tempered clay that dried over time or during

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firing. It is this ceramic lining that vitrifies during smelting, forming a “slag skin.” Slag bubbling out of the smelting crucible could also have dripped down onto the clay lining of the bowl. In addition, it should be noted that at the KSOMD sites, clay-lined bowls were excavated with the clay lining in place, but only around the mouth of the bowl, where the lining had been smoothed out to make a flat surface surrounding the bowl. However, no clay-lined bowl was found that had a vitrified lining in place, due most probably to the thinness, hence friability, of the slag skin as well as the looseness of the crushed gravel matrix to which it had to adhere. The frequency of what are seen as slag skin bowl fragments is attributed to their friability and their role in innumerable smelting events that took place over the centuries at the site. The LoRAP reconstruction of the smelting installation shows a chimney positioned at site surface level atop a clay-lined insulation bowl, with the charged crucible placed inside the chimney (Ciarla 2008:334–335, fig. 31; see Figure 2.29 below). The excavators also argue that “slag, once skimmed from the crucible, would adhere to the nearest portion of the insulating bowl, i.e., the rim and the wall, not the bottom of the bowl which was presumably occupied by the base of the crucible and protected by the burning residue of the fuel” (Ciarla 2008:335).

Figure 2.29  Hypothesized reconstruction of a typical smelting installation from the sites of Khok Din and Noen Din in the KSOMD. This reconstruction may also be typical of those that existed at Nil Kham Haeng (adapted from Ciarla 2008:335).

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It also is possible, given the temperatures reached during the smelting process (ca. 1250°C) that the fabric of the interior of the bowl would vitrify whether or not slag was being skimmed or dribbling from the crucible. The chimney sitting atop the bowl was, therefore, never in contact with the crucible charge, i.e., the chimney was never charged full of ore and charcoal. It served primarily as a stack. This is why, it has been suggested by the excavators, that the excavated chimneys, intact and fragmentary, never show any slagging or vitrification (cf. Pryce 2009; Pryce et al. 2010:249). The Noen Din chimney interior appeared “harder and lighter in colour than the rest of the body due to over-heating because it was quite close to the charcoal (or dry wood) burning over the charge of the ore” (Ciarla 2008:332). The crucible from Noen Din, reconstructed by the excavators, shows an almost straight-sided, cylindrical beaker with an exterior rim diameter of about 10.5 cm “with a round to flat lip and relatively thick walls (1–3.5 cm)” (Ciarla 2008:334, fig. 30; see Color Fig. 2.30). A possible beaker was excavated in a Nil Kham Haeng burial abutting a disassembled but complete chimney. The exterior has at least three splashes of greenish dross adhering to it, but that is all. It is thought that such vessels are not domestic in nature (Fiorella Rispoli, pers. comm.). Moreover, these vessels are of a shape that would fit inside a chimney, although they appear too small to contain a smelting reaction. During the Nil Kham Haeng excavation, the beaker sherds were classed among domestic potsherds, so a future attempt will have to be made to isolate them for further study. There is a second hypothesis, mentioned earlier, for the possible mechanism of smelting and related archaeological evidence at these sites. It holds that slag skins are simply friable, eroded smelting crucible sherds. At Nil Kham Haeng, where slag skins were first identified, it was not possible to ascertain, from excavation, whether there were clay-lined bowls present (see discussion above for more on slag skins). A restudy of Nil Kham Haeng materials in comparison with those from the KSOMD sites with a view to testing these hypotheses would add clarity to understanding the processes involved. The copper-smelting sites of the KSOMD are important because of their metallurgy-related finds and their close technological parallels with Nil Kham Haeng in the KWPV. Khok Din and Noen Din are

composed of lenses of finely crushed ore and slag and share the same repertoire of metallurgical artifacts as does Nil Kham Haeng. A Noen Din burial yielded nine bivalve molds as a “symbolic” grave offering; in a second burial the presence of an example of the enigmatic chimneys indicates an additional and strong technological connection to much larger Nil Kham Haeng. The LoRAP team dated the main occupation phase at Noen Din to ca. 200 B.C.–A.D. 300. (Ciarla 2008:330).

Sepon, Laos–A Multi-site, Prehistoric, Mining and Smelting Complex A third Southeast Asian area with sites devoted to prehistoric copper production was discovered in 2006 at a modern copper/gold industrial mining site near Sepon, Savannakhet Province, Laos (106.014°E, 16.966°N). The work is a cooperative enterprise between the Department of Heritage (Laos), James Cook University (Australia), and MMG-LXML mining company from the PRC. Principle investigators are Thongsa Sayavongkhamdy, Viengkeo Souksavatdy, and Nigel Chang. Since 2008, the project has excavated six main mining and processing localities spread over an area of approximately 10 km (E– W) in the greater Sepon area (Sayavongkhamdy et al. 2009; see Pryce et al. [2011a:3311] for a succinct overview of Sepon’s economic geology). This set of sites is termed the “Vilabouly Complex” after the district in which the sites are found (Nigel Chang, pers. comm. 2018). Excavations have been undertaken at Peun Baolo (2008–2012), Dragon Field (2008), Khanong A2 (2009), Malachite Cave (2011), and Tengkham South D (2012) (Tucci et al. 2014:2). Excavation has demonstrated that Sepon localities of Khanong A2, for example, contain mine shafts with a unique hardwood (likely local) lath timbering system. Bamboo baskets were also found. The finds and site features “are indicative of a complete copper production sequence with associated settlement and mortuary evidence” (Pryce et al. 2011a:3310). Initial 14C determinations indicated a period of mining and smelting activity between ca. 200 B.C. and ca. A.D. 200 (Sayavongkhamdy et al. 2009; see Pryce et al. 2011a:3310; cf. Chapter 3 in this volume). Pryce et al. (2014:292) have noted the existence of a single

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iron period 14C determination from Peun Baolo in the range of the 4th/3rd century B.C. Furthermore, the above authors stated that the excavators have reported on burials excavated below the industrial layer at Peun Baolo that are marked by the absence of typical iron period artifacts including iron and glass, suggesting activity prior to ca. 2400 B.P. in the Sepon area. Current published 14C dates range from early 4th century B.C. well into the second half of the 1st millennium A.D.—thus over 1000 years of mining is demonstrated (Nigel Chang, pers. comm. 2018). Artifacts from the lower bronze period Ban Chiang and 1st millennium B.C. Phu Lon show lead isotopic compatibility with the Sepon signature (Dussubieux and Pryce 2016; Pryce et al. 2014; see Chapter 3 in this volume). Recent indications are that ca. 1000 B.C. dates are forthcoming (MMG LXML Sepon 2016).2 Although excavation continues and finds are still being analyzed, the metal-related artifacts are known to include ore fragments, slag, crucibles, molds, ingots, and domestic potsherds, as well as burials (Sayavongkhamdy et al. 2009; see Pryce et al. 2011a:3311–3312, figs. 2, 3, 6). In 2008, a preliminary program of laboratory analysis at the UCL Institute of Archaeology was undertaken by Hayden Cawte (unpublished) on such finds, including 25 crucible sherds from vessels used for smelting and casting, from two primary production locations, Thong Na Nguak, “Dragon Field,” and Peun Baolo, “Crucible Terrace.” Also in the study were ingots, molds, slag, and ore samples. The study was published in an M.Sc. dissertation by Elzbieta Watroba (2012) while Pryce subsampled the study artifacts for lead isotope analysis (Pryce et al. 2011a:3310– 3312); see Pryce et al. [2014:274] for 14C dates for these sites).

Khanong A2 Excavations at the western edge of the modern mine pit yielded ancient mining evidence. Some 107 vertical mine shafts were revealed, with one shaft extending ca. 23 m deep without reaching sterile soil. The mine shafts ran between 1.1 m and 2.5 m in diameter. Several meters of the orebody were exposed at the base of the shaft. Shafts were often dug nearby one another, but some shafts actually cross-cut other

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shafts. Timbers of local hardwood bound with rattan supported the shafts, which had walls comprised of sheets of bamboo or rattan matting between the timbers and the surrounding clay matrix. These organic materials were excellently preserved by anaerobic conditions and the high level of copper salts in the clay. The excavators suggested that mining may have continued at this site for some 250 years. (See Tucci et al. [2014:5 and fig. 3] for details on the timbering system and a potential link to the 1st millennium B.C. copper mine at Tonglüshan in China.)

Tengkham South D At this site, excavation took place some 10– 20  m below ground surface on an artificial terrace under so-called rapid response conditions due to pending mining activity, discovering three separate mining-related installations. First were well-built circular, timbered shafts similar though not identical to those at Khanong A2. Second, two square shafts (2.2 x 2.2 m) were revealed, which had interior walls of vertical split-hardwood pieces fitted between the vertical pieces to form the framing that supports the shaft, with the probable purpose of preventing caveins (Tucci et al. 2014:6). Third, excavators encountered, well below the surface, a possible ancient open pit mine area, which over time had gradually been filled in by eroding soil. Though they have yet to be identified, enigmatic tube-like artifacts made of iron were excavated at this locus. On the edge of the mining area at Tengkham South D (hereafter TKSD), a unique discovery of two well-preserved dugout canoes was made; the canoes may well have been coffins, though the acidic soil prevented bone preservation. Based on the assumption that these were coffins, the excavators propose that miners and mines were strongly and personally linked. This interpretation would be consonant with a mining system composed of small, kin-based groups (Tucci et al. 2014:9). According to geologists who have for years investigated the Vilabouly Complex, it is possible that the area of the Dragon Field was also a large open pit mine that was buried by natural processes over time. Ancient open pit mining, on this scale, at Sepon is currently the best example of this practice in Southeast Asia, though it may have been practiced at Phu Lon as

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well. Future research should reveal more about the nature of this activity, which might involve larger mining teams working in a more coordinated fashion to mine a deep pit (cf. Pigott 1998). With regard to Pryce’s SEALIP research, it has been noted that the large, slagged crucibles from Peun Baolo resemble the large Non Pa Wai crucibles far more closely than they do the small, spouted “common Southeast Asian crucible” prevalent in prehistoric northeast Thailand (see Pryce et al. 2011a:3311, fig. 3). The Peun Baolo reconstructed crucible measures 18 cm in diameter and is about 8 cm tall, similar in width but shallower than the complete, more hemispherical example from the Non Pa Wai bronze period. Three slag fragments from Peun Baolo and two slag fragments and a single distinctive plano-convex ingot from Thong Na Nguak, part of the above-mentioned metallurgical assemblage, were sampled by Pryce for LIA from the Sepon artifacts in London (Pryce et al. 2011a:3312, fig. 6). Pryce and colleagues (Pryce et al. 2011a:3314) stated that the Sepon (and Phu Lon and KWPV) “copper production systems can be distinguished with a high level of certainty.” The five slag samples from Sepon were seen to cluster so tightly so as to not allow discrimination between the two Sepon locales under study. The copper-base ingot plotted “at the core of the Sepon field, lending support to its being a primary production ingot” (Pryce et al. 2011a:3315 and fig. 7). Pryce et al. (2014:282) did indicate that among the Sepon samples he studied, the lead and leaded-copper samples appear to overlap with signatures of “lead minerals of similar geological date.” SEALIP’s documentation of a strong link between the Sepon deposits and copper-base metal artifacts from the lower Early Period at Ban Chiang and related sites, dating older than the published Sepon deposits excavated so far, is explained further in Chapter 3. It is also worth mentioning the evidence for LIA links between Sepon and the northwest Cambodian iron period site of Phum Snay, ca. 500 km to the southeast. About ten of the 14 Phum Snay copper-base artifacts analyzed by SEALIP are “reasonably consistent with the Sepon production field” (Pryce et al. 2011a:3315 and fig. 7; cf. Kakukawa et al. 2008). Additionally, with regard to SEALIP analyses of copper-base metal artifacts from Ban Non Wat, Pryce et al. (2014:292) indicated that two copper-base

adze/axes dating to bronze period contexts of the earlier 1st millennium B.C. are seen to “trend towards the Sepon signature, but cannot be considered consistent with it” (Pryce 2012b:492–493; cf. Pryce et al. 2014:292). As Pryce (2012b:493) pointed out, this is of interest given the temporal gap between currently published Sepon dates from the late 1st millennium B.C. and the centuries-earlier date for the two Ban Non Wat adze/axes. Among the group of ten Ban Non Wat copper-base artifacts dating to that region’s iron period ca. 420–200 B.C. “there are reasonable matches with the Sepon copper production signature,” which in turn appears to corroborate a contemporaneous date for copper production at Peun Baolo. Thus, in assessing SEALIP Sepon results at this juncture, Pryce and colleagues (2014:282) are of the opinion that Sepon ores, or others of similar geological date, were used widely across greater mainland Southeast Asia during the later 1st millennium B.C. Finally, it is clear from the preliminary results discussed above that Sepon joins Phu Lon, the KWPV, and the KSOMD as a primary copper production center of great significance to an increasingly improved understanding of metallurgical technology in prehistoric Laos, Thailand, and Southeast Asia as a whole. In closing, one final point merits mention here as it relates to the sociopolitical context within which Sepon mining was being conducted. Three models have been proposed by Tucci and colleagues (2014:10–12) to address how social complexity might relate to mining activity. First, it is possible that Sepon mining was proceeding within a politically heterarchical context, with access to the mine not controlled by elites. Second, what Tucci et al. (2014:11) have termed an “expansionist Chinese state” was making its presence known across the region. The square mining shafts at TKSD resemble those at the 1st millennium B.C. mining site of Tonglüshan near modern Huangshi, and close to Lake Daye in Hubei Province (e.g., Vogel 1982; Zhou et al. 1988). Might the Sepon mine have been to some degree under sway of Dynastic China? Third, Sepon is located in the Laotian uplands and potentially, Tucci et al. (2014:11–12) suggested, may have been part of a society deliberately keeping its distance from incipient states elsewhere in the greater region. In this regard, see the particularly apropos

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discussions by Tucci and colleagues (2014:10) of James C. Scott’s (2009) The Art of Not Being Governed: An Anarchist History of Upland Southeast Asia. Thus, in this context, they argue that it is possible that through contact with lowland polities, the upland people obtained the fundamentals of mining technology that they then adapted to local Sepon conditions over time. Over the span of a millennium or more sociopolitical circumstances certainly changed. Evidence suggests that Sepon must have had some sort of contact with Southeast Asia’s active trade and exchange that would include interaction of some sort and at some point with Dynastic China to the north (Tucci et al. 2014:12). To what extent was China’s influence being felt at the mine? Might it have extended to China exerting some degree of control over Sepon production? Based on current evidence coming out of Sepon, it seems too early to tell, and one cannot discount the possibility that mining activity at Sepon may simply have been built upon local, community-based production not unlike that which has been argued for at prehistoric production sites in Thailand (see White and Pigott 1996).

Concluding Observations The six sites from northeast and central Thailand and the more recently discovered multi-site copper mining and smelting district at Sepon in Laos discussed in this chapter provide, at present, the best excavated archaeological evidence known thus far for later 2nd/1st millennium B.C. mining and metallurgy in the middle Mekong and Chao Phraya Basins, if not for all of Southeast Asia during this period. Based on the massive size of some of these sites with their abundant archaeological evidence and substantial time depth, they can be considered as probable sources of an important percentage of the copper used in these basins in prehistory. Modern economic geology across mainland Southeast Asia indicates that significant quantities of copper (and tin) would have been available in prehistory (TAM 2A, fig. 6.4). Copper deposits, for example, virtually ring the Khorat Plateau of northeast Thailand, while tin concentrates, for the most part, in western Thailand, south into Malaysia, and in Laos and Vietnam (see TAM 2A, fig. 6.4). Although prehistoric copper mines most likely exist elsewhere in Southeast Asia,

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the mines at Phu Lon and those near Lopburi and at Sepon constitute the only sites known currently where copper ores were being extracted in the middle Mekong and Chao Phraya Basins in prehistory. At these sites, copper smelting loci are either on the grounds of the mine, as at Phu Lon, or in proximity. Thus, understanding the archaeology of both mining and primary production sites and reconstructing their chaînes opératoires are essential to comprehending the full scope of the technological systems employed to produce copper and copper artifacts across these two basins. Certain artifact types and/or production practices at these sites appear to link the regions. Crucible smelting is the dominant copper-base metal extraction technology. Casting of socketed implements generally involves the use of bivalve molds either in stone (primarily from northeast Thailand) or ceramic (present in both basins). A distinctive crucible manufacturing technological system links Phu Lon to several consumer settlements in northeast Thailand and in parts of central Thailand, and a distinctive type of ore processing technology appears to link Phu Lon to Nil Kham Haeng and the KSOMD sites. The practice of marking ceramic bivalve molds, in evidence at Phu Lon (one example), may also link the site to the sites of the KWPV where hundreds of examples are known. In addition, it is the opinion of the author that a noticeable visual similarity exists between the ceramic fabric and some of the basic shapes of bivalve molds from KWPV sites and examples from bronze and iron period Ban Non Wat in southern northeast Thailand (see examples from Ban Non Wat in Higham and Kijngam 2012a:470, fig. 18.29, 481–485, figs. 18.39–18.43, 2012b:26, fig. 2.20). SEALIP analyses also now link Ban Non Wat copper-base artifacts from phase BA2 to the KWPV ore deposits. In addition, two copper-base socketed, cordiform-shaped artifacts (one analyzed as tin bronze), typical of shapes found at Nil Kham Haeng, were excavated from a regional iron period context at Ban Non Wat. One can argue that all of the above links, among others, tie the two regions via a network of trade and/or exchange along which raw copper from the KWPV reached metalworker/ consumers at Ban Non Wat (and possibly other northeast Thai sites), who sometimes alloyed it with tin and cast final products in bronze (e.g., Higham and Rispoli 2014).

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The combined Lopburi regional evidence for copper production clearly signals that minimally over the course of the 1st millennium B.C., there occurred an exponential growth in demand by consumers for this metal; the so-called “Copper Rush.” This accelerating growth is measured in hectares of accumulated production debris at the two massive KWPV sites of Non Pa Wai and Nil Kham Haeng, and there are other mostly unexcavated sites in the KWPV and immediate region exhibiting evidence of copper production as well (e.g., Natapintu 1988). Just how tin bronze fits into this metallurgical picture as it is currently known from the Thai sites in Lopburi and the greater Loei region, and the one Laotian copper production district is unclear. Across the expanse of northeast Thailand, available elemental analyses from excavated metal artifacts from several sites (reviewed in Chapter 4) indicate that tin bronze was the alloy of choice from the point of arrival of the technology in Southeast Asia. This fact is one reason why most scholars believe this technology was transmitted from outside the region. In this regard, early on Joyce White (1988:179, 1997:104) alluded to a potential role that may have been played by Eurasian steppe people in the transmission of tin bronze technology further east and southeast. This was followed by Charles Higham (1996, 2002:166, 2006:19) who keyed on this same possibility. Subsequently, Andrew Sherratt’s (2006:43–44) revelatory discussion of what he termed the “Trans-Eurasian Exchange” forged an even stronger link between steppe people and metallurgical transmission to Southeast Asia. However, it was an article published by the author and Roberto Ciarla (2007), building off Ciarla’s earlier research (Ciarla 2007a), that brought this issue of long-distance technological transmission to the fore and opened the floodgates for discussion (e.g., beginning with White and Hamilton [2009, 2014]; then Pryce et al. [2010]; Higham et al. [2011a]; Ciarla [2013]; and most recently Pigott [2018]). At this juncture the jury remains out on peoples involved and routes followed, and only future “ground truthing” via survey, excavation, and laboratory analyses is going to ultimately tell the tale. Analyses currently available for central Thailand, and in particular for the KWPV sites, suggest that these locations were producing primarily copper, which was being sent elsewhere for consumption

and/or alloying and casting to final products. In this regard, Pryce and colleagues have provided one hypothesis for the origins of copper-base metallurgy in the KWPV. They propose “the processes of adoption of foreign technology and local innovation of technology as the most plausible explanations for the appearance of the NPW smelting process” (Pryce et al. 2010:260). It is not clear why metalworkers chose to produce mostly copper and not bronze (on any scale) in the KWPV. After all, tin from western Thailand, if known about, could have been brought in for bronze production. As Pryce and colleagues hypothesize, the adoption of metallurgy may have been a selective process involving a familiarity with metal borne of contact with imported, exotic metal artifacts that were precursors of the technological know-how itself, though this observation is not based on stratigraphically defined evidence (Pryce et al. 2010:260; see also Roberts et al. [2009:1013] on imported metal artifacts as “exotica”; compare Rispoli et al. [2013:125–131] for an update on the period of metallurgy’s adoption, i.e., Bronze Age I in the Lopburi region). Recent SEALIP analyses have provided some preliminary understanding of where the Thai and Laotian copper-base metal was going. Currently the consumers of the Phu Lon product remain unknown (although see Dussubieux and Pryce [2016]). The KWPV LIA signature so far registers only at Ban Non Wat during phase BA2. The KWPV LIA signature perhaps is being masked by the practice of massive recycling in the later 1st millennium B.C. and subsequently (Pryce et al. 2014). Evidence suggests that tin bronze was produced in modest amounts at Phu Lon, but there is no current evidence for its production at the KWPV/KSOMD sites. Future analyses of the KSOMD metallurgical remains under the direction of Pryce may shed new light on this issue. There is so far no evidence for production of tin bronze at Sepon in Laos, although copper-base artifacts that were likely tin bronze were recovered from the excavations of regional iron period contexts (Nigel Chang, pers. comm. 2018). However, tin bronze was being made and cast into a variety of ornaments and implements at various settlements in northeast Thailand from the bronze period on. Evidence for tin bronze production in central Thailand, where copper production predominates, is still elusive at the region’s smelting sites, though, as discussed,

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two confirmed tin bronze artifacts (assumed to be imports) were excavated at Nil Kham Haeng and traces of tin were identified in smelting slag from this site. Northeast Thailand remains a likely candidate for the consumption of central Thailand’s raw copper, and parts of Myanmar (e.g., Nyaung-gan) have also been suggested (Dussubieux and Pryce 2016). Which tin deposits were being exploited for such bronze production is yet another unanswered question for mainland Southeast Asia. A final point with regard to the KWPV copper-producing sites discussed herein is that there are very few iron artifacts or evidence for iron smelting known from their prehistoric contexts, although these sites have settlement and mortuary contexts that postdate the appearance of iron in other parts of Thailand. Why this is the case remains unclear. The relationships of prehistoric copper production in Thailand to copper production and use in surrounding regions are and will be of long-term interest to more than just Southeast Asian specialists (e.g., Chiou-Peng 2018; Hillman et al. 2015). Proposals for the role of parts of today’s PRC as well as potential routes and processes integral to the initial transmission of tin bronze technology to Southeast Asian have been treated at length in print elsewhere (e.g., Ciarla 2007a, 2013; Higham et al. 2011a; Pigott and Ciarla 2007; Pryce et al. 2010, 2014; Rispoli et al. 2013; White and Hamilton 2009, 2014). Evidence is increasingly apparent from the 1st millennium B.C. and possibly earlier for shared technological similarities between sites in Thailand and those that lie well to the north and northwest in the realms of what is today modern PRC and the eastern Eurasian Steppe. But one example comes from the evidence for so-called “founder’s burials” that in the PRC date from the late 2nd to the early 1st millennium B.C. in the regions extending from the Yellow River valley, southern PRC, and into mainland Southeast Asia (Ciarla 2007a:317–319; Rispoli et al. 2013:125, 129). Such burials are earlier on the Eurasian Steppe (e.g., Pigott and Ciarla 2007:82, 84). In addition, the occurrence at sites in the PRC of a certain artifact type, the mold plug for creating cast sockets, was cited earlier in this chapter; the mold plugs from mid-2nd millennium B.C. Erligang Zhengzhou and from Huoshaogou ca. 1000 B.C. are technologically and typologically comparable to those from iron

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period Ban Non Wat and from 1st millennium B.C. KWPV and KSOMD sites. Though there exists a considerable time gap between the regions, use of the mold plug was part of the metalworker’s technological system in northern PRC early on and appeared subsequently in northeast and central Thailand. Although speculative, one can suggest that there is a chronological sloping horizon from the north to the south where this artifact type could have been transmitted along various routes heading south as part of the practice of casting sockets on implements and weapons in bivalve molds. The SEALIP research of Pryce and colleagues has noted that many of their LIA samples could not be identified with any known ore source in Southeast Asia (Pryce et al. 2014). They suggest that sources in southern PRC be investigated for possible links. The rich and closer copper sources in northern Laos among other copper sources in the Loei and Truong Son Fold Belts (see TAM 2A, fig. 6.3) also should be investigated for evidence of prehistoric exploitation. In closing, the extent to which the Lopburi region’s substantive copper production helped to meet the needs of surrounding, regional metal consumers during the 1st millennium B.C. remains to be fully clarified. This and many other questions remain unresolved as Southeast Asian archaeology progresses towards an ever-improving understanding of the interconnectivity of peoples and cultures in relation to the technology of metallurgy during later prehistory in Thailand, Laos, Myanmar, and additional points north, east, west, and south. NOTES: 2.1  This chapter is dedicated to the memory of William W. Vernon and Andrew D. Weiss whom TAP lost in 2018 and 2019. Bill, a geologist, (M.A., Penn Anthropology, 1984) pioneered the study of Southeast Asian crucibles at Phu Lon and Ban Chiang and studied Phu Lon and KWPV ore geology and excavated ceramics. Andy Weiss (Penn BAS, 1980, Anthropology/Engineering), a high school Ban Chiang Project volunteer, worked at MASCA (Museum’s Applied Science Center for Archaeology) founding its ‘Apple Orchard’ computer lab and creating the pioneering COMPASS total station program. He helped to create TAP and served as its Field Director between 1986–1994 and as Senior Excavator at Nil Kham Haeng. He was the driving

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force behind the TAP AMS 14C-dating program, the results of which he completed just before his untimely death. Bill and Andy’s tireless efforts on behalf of TAP are reflected in this chapter. We have lost two special friends and superb colleagues. TAP will not be the same without them. 2.2  Nigel Chang (pers. comm. 2016) indicates he will support the ca. 1000 B.C. date claims (in MMG LXML Sepon 2016) with a forthcoming refereed publication. He is confident that the Vilabouly Complex will sit alongside Khao Wong Prachan and Phu Lon with similar dating. He notes that Vilabouly exhibits a very long continuation of mining using a very specific local methodology to the 7th or 8th centuries A.D.

ACKNOWLEDGMENTS To begin with, I would like to offer my profound gratitude to Joyce White and Elizabeth Hamilton, who in the long-term process of conceptualizing, organizing, and creating this all-important monograph, spent inordinate amounts of time on the editing and improving of this chapter. It is all the better for their dedicated efforts. In addition, I would like particularly to thank Surapol Natapintu who has served graciously as TAP co-director over many years. From the outset, his fieldwork efforts and scholarship have been instrumental to the success of TAP research. The assistance of the Thai Fine Arts Department and the National Research Council facilitated our fieldwork in country and their role is gratefully acknowledged. The late William W. Vernon, beginning in 1985, devoted his efforts to the study of the geology, crucibles and ceramics from the Phu Lon Complex. In 1988 he led the survey team in the KWPV studying its local ore geology and subsequently undertaking thin-section petrography of excavated ceramics. His contribution to TAP research is inestimable. Special thanks go to Fiorella Rispoli and Roberto Ciarla, Senior Excavators at Non Pa Wai and other TAP sites, whose long field experience has resulted in their acquiring an intimate knowledge of TAP site stratigraphy, contexts, and artifacts. Their selfless dedication to the project over many years resulted in the publication of the first working chronology for the Lopburi region of central Thailand (Rispoli et al. 2013). Simply put, their participation has been invaluable. Similarly,

Judy Voelker, who has been a TAP mainstay since our Non Mak La season, and her undergraduate students have, over a number of study seasons, made substantive contributions to organizing and recording TAP material culture housed in the King Narai National Museum in Lopburi and on loan to TAP at the Penn Museum in Philadelphia. Andrew D. Weiss, who directed the on-going TAP AMS 14C dating program until his untimely death, had a formative role in TAP’s conception, computerization, and served as its Field Director and Senior Excavator at Nil Kham Haeng. TAP will simply not be the same without him. In this regard, without the long term, active participation of project archaeobotanist Steve Weber and most recently that of two of his colleagues, Jade d’Alpoim Guedes and Sydney Hanson, the dating program, which is heavily seed sample based, would not have gotten off the ground. In turn, the radiocarbon expertise of Tom Higham and Katerina Douka at Oxford’s Radiocarbon Accelerator Unit assisted by Charles Higham and funded by a major grant from the Marsden Foundation have made the TAP’s involvement in the dating program possible. Thomas Oliver Pryce’s ground-breaking archaeometallurgical research, from his Ph.D. dissertation onward, has provided TAP with a nuanced understanding of the remarkable evidence documenting a major, regional, prehistoric copper production center in the KWPV and its environs on the Lopburi Plain of central Thailand. TAP researchers Lisa Kealhofer (palaeoenvironment), Karen Mudar (faunal analysis), and Chin-hsin Liu (bioarchaeology) continue to make significant contributions to on-going project research. Also, I would like to thank Dr. Nigel Chang, James Cook University, Townsville, Queensland, Australia for his permission to discuss preliminary results of the fieldwork he and colleagues are directing at Sepon, Laos. Finally, TAP researchers wish to extend our gratitude for financial support for fieldwork and post-excavation research contributed by the National Science Foundation, the National Geographic Society, the American Philosophical Society, the American Council of Learned Societies/ Luce Foundation, the School for Advanced Research, the Penn Museum, and Northern Kentucky University. During TAP’s decade in the field, the patronage of the late Ms. Betty Starr Cummin of Philadelphia facilitated our fieldwork significantly.

3 Lead Isotope Characterization and Provenance of Copper-base Artifacts from Ban Chiang and Don Klang T. O. Pryce

T

he 297 copper-base artifacts excavated at Ban Chiang and the 89 from Don Klang have been extensively studied by Ban Chiang Project researchers for their typological, microstructural, and elemental compositional characteristics (see TAM 2B, chapters 2, 3, and 4). Data were previously posted online by the Ban Chiang Metals Project in 2007 (in 2016 replaced by http://db.iseaarchaeology.org/metals-database/). These data have allowed useful comparisons with other regional assemblages for consumer preferences, artifact types, alloying traditions, and working techniques (see Chapters 2, 4, 5, 6, this volume; Vernon 1997; White and Pigott 1996). Additional information for the reconstruction of Ban Chiang culture area metallurgical production and consumption behaviors can be provided by the geochemical characterization of geological regions and archaeological materials. The data patterning from different stages of the metal production and consumption sequence can be used to “provenance,” or locate a probable source or sources, of those materials. These links enable archaeometallurgists to reconstruct metal exchange networks but more fundamentally permit the identification of social interactions between metal producing and consuming populations, which might not otherwise be evidenced (see e.g., Brill and Wampler 1967; for other regions, see Pollard [2009]; Wilson and Pollard [2001]). The most effective analytical methodology currently available to provenance copper-base objects is Lead Isotope Analysis

(LIA) combined with elemental compositional data. Archaeological LIA operates on the basis that sufficient variation must exist in the lead isotope signatures of regional metallogenic deposits, a function in part of their geological age, that they can be reliably distinguished through the ratios of lead’s four stable isotopes 204Pb, 206Pb, 207Pb, and 208Pb. If these mineral bodies, usually copper, lead, or tin-bearing, have been exploited in the past, then their respective lead isotope signatures will have been transmitted without significant modification into the resulting raw metal (Budd et al. 1995). Therefore, analysis of the lead isotope signatures of metal artifacts can potentially identify the origin of metal found in excavated contexts and reconstruct ancient regional metal supply networks (e.g., Hirao and Ro 2013; Pryce 2012a; Pryce et al. 2011a, 2011b, 2014). However, there are some large caveats to archaeometallurgical provenancing using LIA. Firstly, lead isotope ratios for geographically separate mineralizations may overlap if they formed at a similar period in geological time. Secondly, lead isotope signatures of copper from a single mine may vary greatly if there were chronologically sequential mineralization episodes. Thirdly, lead isotope ratios in individual artifacts are susceptible to modification due to processes of blending (e.g., mixing copper from different sources), alloying (e.g., copper combined with tin and/or lead), and recycling (remelting copper-base artifacts for reuse). Finally, and of great importance,

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2C: METAL REMAINS IN REGIONAL CONTEXT

minerals of different types and from different sources have highly variable lead contents, meaning that the LIA signatures of the resulting more lead-rich metals will overwhelm those of relatively lead-poor metals (e.g. Pollard 2009; Pryce et al. 2014). In short, relating an artifact’s lead isotope ratio to a specific ore source can be full of potential pitfalls. Nevertheless, archaeometallurgical LIA is an established methodology whose effectiveness has been proven in numerous cultural theaters: the Mediterranean (e.g., Gale and Stos-Gale 1982; Stos-Gale and Gale 2009); the Middle East (e.g., Weeks 2003; Weeks et al. 2009), and Europe (e.g., Bray and Pollard 2012; Müller et al. 2007; Pernicka et al. 1993). It was in light of LIA’s potential to reconstruct metal exchange networks as a proxy for regional social interactions that the Southeast Asian Lead Isotope Project (SEALIP) was established in 2009 (Pryce 2012a; Pryce et al. 2011a, 2011b, 2014). The copper-base metal assemblage from Ban Chiang, one of the bestknown sites in the region, was naturally an important addition to the database. Lead isotope analysis is a relatively expensive technique, so it was not feasible to conduct LIA on all the artifacts from Ban Chiang and its neighboring sites, but the results of this preliminary geochemical characterization and provenance study have revealed some very interesting patterning in the localization and potential dating of the metal supply to the Ban Chiang culture area.

Methodology Many of the complete artifacts excavated from Ban Chiang and Don Klang are on exhibit in Thailand. However, as described in TAM 2B, chapter 2, samples of many of the exhibited artifacts, as well as of metal artifacts on loan from the Thai government to the Penn Museum, have been studied elementally and metallographically over the years. For the LIA study, subsamples from these existing samples were obtained for elemental and isotopic analysis as part of the SEALIP program. The sampling strategy was intended to give a diachronic perspective from lower “Early Period” to “Late Period/Protohistoric” contexts at Ban Chiang (17 samples) and Don Klang (3 samples), also taking into account different artifact typologies, artifact uses, alloying, and working traditions (Table 3.1). Small (1–2 mm3) subsamples were

generally cut from the mounted blocks of the previously studied artifacts with a 0.2 mm jewelers’ saw blade. Potential environmental contamination from lead-bearing groundwater can have an impact upon confidence in the resulting data, so the visible degree of corrosion seen in the cut samples was recorded as follows (Table 3.1): shiny extant metal is “low,” black copper oxides are “medium,” and green copper hydroxides are “high.” The samples were then analyzed for elemental and lead isotopic composition at the Curt-Englehorn-Zentrum Archäometrie (CEZA) in Mannheim (Germany), using an X-ray fluorescence spectrometer (XRF) and a VG Elemental Axiom Multi-Collector Inductively-Coupled-Plasma Mass-Spectrometer, respectively (MC-ICP-MS), as per CEZA’s established protocol (Niederschlag et al. 2003), and as used for other SEALIP samples (Pryce 2012a; Pryce et al. 2011a, 2011b, 2014).

Results1 For the present geochemical characterization/ provenance exercise, the primary purpose of the elemental data (Table 3.2) is to distinguish between copper or lead exchange systems, as identified by LIA. Nevertheless, these data also clearly indicate that five alloy groups exist within the sampled Ban Chiang and Don Klang assemblages: bronze, leaded bronze, leaded high-tin bronze, leaded copper, and high-tin bronze; there is also a possible arsenical bronze (BC5)2. These groups show some chronological variation; although, in the studied sample, standard bronze (2–17 wt% Sn) is present in all periods, leaded bronzes appear in the Middle and Late Periods, and high-tin bronzes (20–32 wt% Sn) are confined to the Late and Late–Protohistoric Periods. The lead isotope data (Table 3.3, Color Fig. 3.1) suggest that several primary production and/or secondary recycling systems are responsible for metal supply to the Ban Chiang culture area. Of the nineteen samples for which lead isotope data are currently available, five Ban Chiang (BC1, BC4, BC6, BC11, and BC12) and two Don Klang (DK2 and DK3) may be considered “provenanced” in that they appear consistent with the Sepon copper production system in central Laos, as defined in Pryce et al. (2011a). It is noteworthy that BC1 is from the lower (earlier) Early Period, and BC4 and BC6 are from the upper

LEAD ISOTOPE CHARACTERIZATION AND PROVENANCE

59

Table 3.1  Artifacts from Ban Chiang and Don Klang Selected for Lead Isotope Analysis

SEALIP ID

BC Artifact ID

Period

Corrosion

Artifact

SEALIP/TH/BC/1

BCES 762/2834

Lower Early Period IIIa Low

Cu-base socketed spearhead with bent tip

SEALIP/TH/BC/2

BCES 596A/1984

Lower Early Period IVc Low

Cu-base bangle

SEALIP/TH/BC/3

BCES 596B/1984

Lower Early Period IVc Medium

Cu-base bangle

SEALIP/TH/BC/4

BC 693D/1203A

Upper Early Period Va

Medium

Cu-base bangle

SEALIP/TH/BC/5

BCES 741/2625

Upper Early Period

Medium

Cu-base tanged arrowhead

SEALIP/TH/BC/6

BC 679A/1071

Upper Early Period

High

Cu-base bangle

SEALIP/TH/BC/7

BCES 1402/1320

Middle Period VIIa

Low

Cu-base dual phase amorphous fragment (leaded bronze)

SEALIP/TH/BC/8

BCES 1402/1320

Middle Period VIIa

Low

Cu-base dual phase amorphous fragment (copper*)

SEALIP/TH/BC/9

BCES 591/1981

Middle Period VIIa

Low

copper-base T-section undecorated bangle

SEALIP/TH/BC/10

BCES 395A/1115

Middle Period VIII

Low

Cu-base bangle

SEALIP/TH/BC/11

BCES 2020A/1982

Middle Period

Low

Cu-base crucible prill

SEALIP/TH/BC/12

BCES 2020B/1982

Middle Period

Low

Cu-base crucible prill

SEALIP/TH/BC/13

BC 987A/1005A

Late Period

Low

Cu-base crucible prill

SEALIP/TH/BC/14

BC 987B/1005A

Late Period

Low

Cu-base crucible prill

SEALIP/TH/BC/15

BC 2161A/781

Late Period X

High

Cu-base wire

SEALIP/TH/BC/16

BC 2207/355

Late Period

Low

Cu-base knob-shaped fragment

SEALIP/TH/BC/17

BCES 237/516

Late Period

Medium

Cu-base flat fragment

SEALIP/TH/DK/1

DK 214/388

Late Period

Medium

Cu-base bangle

SEALIP/TH/DK/2

DK 151/331

Late Period

Medium

Cu-base wire

SEALIP/TH/DK/3

DK 109/287

Late Period/ Protohistoric

Medium

Cu-base flat fragment

*Presumed because of its pinkish color. No elemental or isotopic data exist as yet for this phase of the sample due to a misunderstanding between the author and laboratory staff in Mannheim, but it is hoped that this can be rectified in the future. Note: In SEALIP ID, BC represents both Ban Chiang locales combined (Ban Chiang 1974 and Ban Chiang Eastern Soi 1975); BC = Ban Chiang 1974; BCES = Ban Chiang Eastern Soi 1975; DK = Don Klang; Cu-base = copper-base, exact composition unknown; bronze = at least 1wt% tin.

1.99