Excavations in the Black Earth 1990-1995. Stratigraphy. Vol. 2. Part Three: The Later Part of the Birka Period. Part Four: The Finds 9172098880, 9789172098886, 9789172099036

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B I R K A

S T U D I E S [ 10 ]

Errata To the Reader, When transforming tables 21:2, page 206, and 21:3, page 209, to printing orginals, the computer automatics changed part of their respective content. Tese tables are corrected in this electronic version With apologies Björn Ambrosiani August, 2021

B I R K A

S T U D I E S [ 10 ]

Excavations in the Black Earth 1990 - 1995

Stratigraphy Vol. 2 Part Tree: Te Later Part of the Birka Period Part Four: Te Finds

By

BJÖRN AMBROSIANI

STOCKHOLM 2021

Cover: Carved sphere of crystalline limestone with stylized images including an eagle and wolves probably linked to the mythology and symbolism of the kings of the Uppsala dynasty. Eighth century AD. Scale approximately 1:1. Photo and digital colour interpretation by Carl O Löfman.

BIRKA STUDIES 10

© Text: The Author © Pictures: The Photographers, Illustrators, Acknowleded Sources, and The Birka Project Layout: Phyllis A. and Björn Ambrosiani, The Birka Project Cover: Phyllis Anderson Ambrosiani Produced by The Birka Project for Riksantivarieämbetet Printed 2021 by TMG Tabergs, Växjö ISBN 978-91-7209-888-6 ISBN 978-91-7209-903-6 (PDF)

CONTENTS List of illustrations ..................................................................7 Foreword and Acknowledgements ...........................................9 Introduction Stratigraphy 1990–1995: Volume 2 .................11

Part III: Te stratigraphy in the later part of the Birka period: the northern and southern plots Chapter 11 Additions to BS9: Chapter 8, Phase B5: Workshop with House in the Eastern Part................................14 Introduction.......................................................................14 Sub-level B50S Furnace in the southern plot.....................16 Sub-level B57 Yard, house gable, and waste.......................19 Sub-level B58 Waste layers................................................23 Sub-level B59 Waste and ash layers....................................25 Chapter 12 Phase B6: Destruction layers with traces of buildings..................................................................28 Introduction.......................................................................28 Sub-level B61 Scattered ash layers and a possible building..31 Sub-level B62 Destruction and waste layer........................33 Chapter 13 Phase B7: Buildings and fre layers in both plots Introduction.......................................................................35 Sub-level B71 Ash layers, house gables, and a row of three buildings............................................................39 Sub-level B72 House gable, yard, waste layers, and fre/ash layer...................................................................46 Sub-level B73 House gables(?), yard, waste layers, and fre/ ash layers............................................................51 Sub-level B74 House foundations with hearth, waste layers, digging damage, and hearth/charcoal layers........57 Sub-level B75 Group of posts and destruction layers.........61 Chapter 14 Phase B8: Restructuring with temporary road bank and buildings............................................................64 Introduction.......................................................................64 Sub-level B80 Hearth group B805 in sub-area **6............73 Sub-level B81 Temporary road bank and building.............73

Sub-level B82 Buildings with large hearth B805c, waste and and levelling layers..............................................78 Sub-level B83 Waste layers, damage by later structures, and "Te burnt house"..............................................83 Sub-level B84 Waste in the jetty passage............................91 Chapter 15 Phase B9: Building remains, debris, and ploughdamaged layers in both plots....................................93 Introduction.......................................................................93 Sub-level B91 Waste and ash layers and a building with a post-supported roof..........................................101 Sub-level B92 Transverse ditch and building remains......105 Sub-level B93 "Te northern house", hearth, and humifed waste................................................................109 Sub-level B94 Relayered flling in the passages and in the northern plot...................................................113 Chapter 16 Plough layers, dump, and reflled soil................114 Chapter 17 Stratigraphy and interpretation: Te occupation layers from the period AD 870–970.......................118 Te stratigraphical work ..................................................118 Phases B5–9: Plots, boundaries, buildings, and passages, or alleys .....................................................................119 Buildings and chronology ................................................130 Large waste layer...............................................................130 Jetty passage, or alley..........................................................131 Northern alley .................................................................131

Part IV: Te Finds in the Black Earth 1990–1995 Chapter 18 Background ……….….....................................133 Hjalmar Stolpe’s fnds from the 1870s .............................133 Finds from 1969–1971 excavations .................................134 Finds from 1990–1995 excavations .................................135 Chapter 19 Category 1: Osteology ….….............................137 Table 19:1: Osteology.......................................................147

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Chapter 20 Category 2: Metal..............................................168 Non-ferrous metal in the Birka stratigraphy......................168 Object groups...................................................................170 Ornaments and fragments decorated in specifc styles.......170 Weapons and weapon parts...............................................176 Utensils: Scales and keys....................................................178 Coins................................................................................178 Weights and weight systems..............................................186 Chapter 21 Weight, weighing, and weights............................193 Background and state of research......................................193 Weight systems.................................................................196 Example 1: Spherical iron weights with a cover of copper alloy from Birka graves...................................201 Example 2: Spherical weights in sets.................................205 Example 3: Cubo-octahedral weights of copper alloy in the Birka graves....................................................210 Example 4: Weights of copper alloy from the Black Earth.213 Example 5: Lead weights from the 1990–1995 excavations in Black Earth................................................224 Discussion........................................................................239 Hypothetical conclusion...................................................254 Chapter 22 Category 3: Bone and antler...............................256 Combs..............................................................................256 Chapter 23 Category 4: Glass and semi-precious stones........264 Glass beads.......................................................................264 Beads of semi-precious stones...........................................280 Amber..............................................................................285 Hollow glass and fat glass.................................................287 Production of glass beads in Birka.....................................291 Summary..........................................................................293 Chapter 24 Category 5: Clay, moulds, and textile tools........295 Introduction.....................................................................295 Te workshop fnds: stratigraphic perspectives..................296 Loom weights and spindle whorls.....................................303 Chapter 25 Category 6: Stone; Category 7: Burnt clay (daub); Category 8: Slag; Category 9: Miscellaneous, organic matter.........................................................304 Category 6: Stone.............................................................304 Category 7: Burnt clay (daub)..........................................310

6

Category 8: Slag...............................................................312 Category 9: Miscellaneous, organic matter.......................313 Chapter 26 Discussion and evaluation of the 1990–1995 excavations in the Viking Age town of Birka............314 Introduction.....................................................................314 Stratigraphy and chronology.............................................314 Variations in jewellery and beads bet at trading sites..........316 Weights and weight systems..............................................316 Objects from the Near East: eastern or western import routes?....................................................................317 Contacts with Byzantium and the Caliphate....................318 Contacts with the Arctic Sea to the north-west and with southern Norway............................................318 Te people of Birka..........................................................319 Te southern plot-eastern contacts?................................320 How was Birka supplied?..................................................321 Local marketplace or town?..............................................324 Trade: gift economy or market trading?............................325 Birka and the king........................................................... 327 Conclusion.......................................................................329

References..........................................................................330 Appendix 1–4..............................................................343

Introduction.....................................................................343 Appendix 1 List of features and S-units...............................343 Appendix 2 Checklist S–B..................................................374 Appendix 3 Find material per B–feature.............................383 Appendix 4 Guide to the registration system.........................397

Birka Studies, Series Information .........................................398

LIST OF ILLUSTRATIONS

All plans, diagrams, and schemas were produced in ArcMap and Excel by Björn Ambrosiani Introduction Fig. Intr:1. Te division of the site into areas ....................................12

Chapter 18 Fig. 18:1. Te automated sieve .......................................................132

Chapter 11 Fig. 11:1. Te lower part of the blast furnace B50S5a .......................16 Fig. 11:2. Soot and charcoal in front of the furnace B50S5 ...............18

Chapter 19 Fig. 19:1. Total weight of bones per sub-level ..................................137 Fig. 19:2. Cattle bones, kg per sub-level ..........................................138 Fig. 19:3. Pig bones, kg per sub-level ...............................................138 Fig. 19:4. Sheep/goat bones, kg per sub-level ..................................139 Fig. 19:5. Bird bones, kg per sub-level .............................................140 Fig. 19:6. Fish bones, kg per sub-level. ............................................141 Fig. 19:7. Horse bones, 10 g per sub-level........................................142 Fig. 19:8. Bones of wild species, 100 g per sub-level ...........................143 Fig. 19:9 a–b. Relative distribution; meat animals per sub-level ...... 144 Fig. 19:10. Relative species distribution by sub-level .......................145 Fig. 19:11–12. Bengt Wigh ............................................................146 Fig. 19:13. Accumulation of bones in S3412 R7310 ......................156 Fig. 19:14. Te bones after cleaning ...............................................156 Fig. 19:15. Te bone fnds from S39 in B735/745 .........................160

Chapter 13 Fig. 13:1. Te corner hearth S3358 in B71S1 ...................................42 Fig. 13:2. Te sills in the square building B71S1 ..............................43 Fig. 13:3 Cornerstone in B71S1.......................................................57 Chapter 14 Fig. 14:1. Te “burnt house” B83S2 with wooden sills ....................65 Fig. 14:2. Hearth S858 in B83S2 .....................................................65 Fig. 14:3. Te large stone sill S3591 in the southern plot .................66 Fig. 14:4. A fence along the plot boundary or a wall? .......................66 Fig. 14:5. Te sill trench B835a with building oferings ...................67 Fig. 14:6. Te building ofering R3283 F43283–4 ...........................67 Fig. 14:7. Antler for making combs in the southern plot ............... ..68 Fig. 14:8. “Comb” composed of pieces of A and B combs ...........,.....68 Chapter 15 Fig. 15:1. Stone terrace S110. ...........................................................94 Fig. 15:2. Part of the terrace in 1990 in the A-trench ........................94 Fig. 15:3. Row of stake-holes for a fence, AA8 ..................................95 Fig. 15:4. Transverse ditch B925 (formerly AA6) ..............................96 Fig. 15:5. Transverse ditch B925 was redug several times ...................96 Fig. 15:6. Probably Volga Bulgar vessel, in phase B8 and B9 ................97 Fig. 15:7–8. Te large 1991 hoard ....................................................98 Fig. 15:9. Te falcon mount R2026 F40465 .....................................99 Fig. 15:10. Post-hole S1002 in building B91S1–2a .........................102 Fig. 15:11. Post-hole S1801 ............................................................103 Fig. 15:12–13. Te large central hearth in building B91S1–2a .......103 Chapter 16 Fig. 16:1. Cross with arms of Valsta type, R1548 F39838 ..............115 Chapter 17 Fig. 17:1. All features reported in Chapters 11–15 .........................120 Fig. 17:2. New diagram presenting features and fnds for all units...121 Fig. 17:3. All buildings observed during the 1990–1995 excavations.122 Fig. 17:4. Special building B91S1–2a .............................................124 Fig. 17:5 Corner hearth S3396 in B72S1 ......................................126

Chapter 20 Fig. 20:1. Gold foil with fligree decoration, R3414 F43901 ...........169 Fig. 20:2 a–b. Silver objects, R3018 F33096 and R3306 F88914.......169 Fig. 20:3 a–b. Tin pendants, R2430 F33096 and R2650 F42051.... 170 Fig. 20:4. Stratigraphic diagram of brooches ...................................171 Fig. 20:5. Stratigraphic diagram other jewellery forms, 1990–1995..173 Fig. 20:6 a–b. Equal-armed brooches, type Aagård B, R4059 F50266 and F50267 .................................................174 Fig. 20:7. Double mould for equal-armed brooches, R1890 F34102 .....................................................................174 Fig. 20:8. Model for Valsta brooches, R8305+R3906 F74577+51664 .....................................................................175 Fig. 20:9. Stratigraphic diagram of Tor’s hammers and amulets ....177 Fig. 20:10. Stratigraphic diagram of weapon details ........................179 Fig. 20:11. Stratigraphic diagram of scales and keys ........................180 Fig. 20:12. Stratigraphic diagram of Islamic coins, year of minting ..183 Fig. 20:13. Stratigraphic diagram of Islamic coins, dynasty .............184 Fig. 20:14. Stratigraphic diagram of other coins ..............................185 Fig. 20:15. Stratigraphic diagram of spherical weights ......................188 Fig. 20:16. Stratigraphic diagram of cubo-octahedral weights ...........189 Fig. 20:17. Stratigraphic diagram of lead weights ...........................190 Fig. 20:18. Weights from the 1990–1995 excavations........................192 Chapter 21 Fig. 21:1. Graphic representation >5 g of the weight systems ..........199

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Fig. 21:2. Graphic representation 210.62 g with 8 pennies per örtug were used. Table 21:1 shows the respective values for the target weights. Tables 21:4a–b and Figs. 21:10–12 show that the recalculated densities provide a clear overview of the weight distributions across the diferent weight systems. Deviations between estimated weights and target weights are usually only a few hundredths of a gram. Often, the weights may be assigned to one weight system. Some exceptions are discussed below. In lists 1–4, Erik Sperber presents 56 objects as cubo-octahedral bronze weights (Sperber 2004 [BS6], 80–83). Tey usually are made of lead bronze. Te density of one pair of weights is so high that it is likely that they are lead weights instead. Some examples lacking proper cubo-octahedral form are excluded here. An analysis of Sperber's remaining 53 weights suggests a preliminary division (Table 4a) into fve main weight systems: V G G or Dh Dh

15 10 8 10

Dh or V S C Undetermined

1 9 1 1

Viking Age mark weight Undoubtedly, the largest weight group includes the "light" Viking Age mark with its background in the early Vendel Period. Fifteen weights belong to this system (Table 21:5). Probably a few more could belong to the Gutnic or the dirham system. All of these groups show close agreement, but they often fall on either side of the target weight. With a density of 8.6, seven weights are heavier than the target weight. Similarly, with a density of 8.7, fve weights are lighter than the target weight. With a density between 8.6 and 8.7, four weights coincide with the target weight. Tis suggests that the density values should be adjusted either to allow for diferences in when the weights were manufactured or erratic efects on the value calculations due to a degree of uncertainty in the measurements. Te other systems do not show the same clear picture. Te series 1p – 1½p – 2p – 2½p – ½ örtug (Table 21:5) should be an appropriate adaptation to the need to weigh payments when trading in goods of lower value such as foodstufs and certain raw materials, for example. Weights in this group are found from phase B6 to phase B9 in the 1990–1995 stratigraphy, i.e. during the period AD 870–970. However, the heaviest weights are found in the later phases of the stratigraphy. Tis may indicate that lighter, smaller denominations were used in the earliest phases.

217

Fig. 21:10 Sj kubooktaeder rekonstr densitet 8,7 H Weight group 3,5–4,8g

4,5

Scale variability 2% = 0,08g = max 0,16g

4,5 4,4 4,3 4,2 4,1

4

4 3,9

½ örtug S 1 Mitqual ½ örtug G 1½ Dirham ½ örtug V

4,39g 4,27g 4,248g 4,23g 3,95g

3,8 3,7 3,6

3,5

J Weight group 2,4–3,1g

Scale variability 2% = 0,06g = max 0,12g

3,4 3,3 3,2

3

3,1

¾ Mitqual

3,202g

3 2,9 2,8 2,7 2,6

2,5

2,5 2,4

K Weight group 1,5–2,3g 2

2,3 2,2 2,1 2 1,9 1,8

1,5

1,7 1,6 1,5

1

L Weight group 0,7–1,5g 1,5 1,4 1,3

3pV 4pG 1 Dirham 2½ p S 2½ p V

2,966g 2,832g 2,82g 2,745g 2,467g

Scale variability 2% = 0,04g = max 0,08g 2pS 3pG ½ Mitqual ¾ Dirham 2pV

2,195g 2,124g 2,115g 2,115g 1,975g

2½ p G 1½ p S

1,77g 1,647g

1½ p V

1,481g

Scale variability 2% = 0,02g = max 0,04g 1½ p V ½ Dirham

1,481g 1,41g

1,2

0,5

1,1 1 0,9 0,8 0,7 0,6

1pS 1pV

1,098g 0,987g

¼ Dirham 1pG

0,71g 0,708g

0,5

0

0

10

20

30

40

50

Fig. 21:9. Cubo-octahedral weights in the Black Earth 1990– 1995, arranged by weight at calculated density 8.7.

218

60

Mitqual Dirham Mark: V(iking) G(otlandic) S(candinavian) Fig. 21:10. Analysis of cubo-octahedral weights in the weight groups H–L in the Black Earth 1990–1995, arranged by weight at calculated density 8.7.

Table 21:5. Weights assigned to the Viking Age mark system. Target weight: Weight of the weights

1p 0,9875g 0,97 0,88 :

1½p 1,481g 1,48-1,49 1,47-1,49 1,48

2p 1,975g 1,97-1,99 1,92 1,945 1,93 1,93

2½p 2,495g 2,50 2,57 2,51 2,56 2,49

3p

½örtug 3,95g 4,00 3,92-3,98 4,03 G?D? 4,01 G?D?

Te role of density values in these interpretations may be considered more closely. Table 21:6 explores the efects of diferent densities between 8.5 and 8.7 on the weight group 2½ pennies Viking Age mark weight. Te best correlating value for each weight is indicated in bold. Table 21:6. Density comparisons. Target weight

Weight nbr

AFLweight

Measured density

207 209 225 233 263

2,18 1,65 2,18 2,45 2,41

7,59 5,52 7,48 8,22 8,43

2½p dens 8,5 2,495g 2,44 2,54 2,48 2,50 2,43

2½p dens 8,6 2,495g 2,47 2,57 2,51 2,56 2,46

2½p dens 8,7 2,495g 2,5 2,6 2,53 2,59 2,49

Two of the fve weights for 2½p V have values that best correlate with density 8.5, one with 8.6, one with 8.7, and one with both 8.5 and 8.6. When the average of each density is calculated, a density of 8.5 fts best with 2.478, and a density of 8.6 fts best with 2.514. It is likely that the weights were manufactured at diferent times which in itself may cause slight diferences in metallurgical densities. For density 8.5 the average is within ±0.06 g, which is well within the margin of error for the scales used at that time. To conclude, this simple analysis gives a clear picture of what an insignifcant change in the density of the casting compound can entail. Another source critical factor involves the measured volume of the individual weights. Any volume loss due to damaged edges, polishing, conservation (Sperber 2004 [BS6], 63 and 70), or for other reasons means that the calculated values for each individual weight, regardless of density, probably will fall below the target weight. Nevertheless, a calculation of the original values of the individual weights using this method may be justifable. It also may be noted that weights that were produced at diferent times likely were cast using compounds of slightly diferent densities. Gutnic weight Table 21:1 shows the values for the high medieval Gutnic mark. According to Nils Ludvig Rasmusson, this mark weighs 204 g and is divided into 8 öre or 24 örtug with each örtug further divided into 12 pennies (Rasmusson 1966). As discussed in connection with Table 21:11, divisions of this weight should be used as the target weight (Table 21:7). Te target

219

weight of the Gutnic mark and the weights in grams of the actual weights coordinate well. With 12 pennies to the örtug in the Gutnic system, denominations such as 3p, 4½p = half of ¾ örtug, and 6p = ½ örtug are natural in the system. Tere is a close link between the dirham and the Gotland weight system. Instead, the weight of 2p may correspond to ½ dirham, and 4 pennies essentially correspond to 1 dirham. Te örtug then is equivalent to 3 dirham. Tese relationships probably led Sperber to believe that most of the weights adapted to the Gutnic standard belonged to the dirham series. However, denominations such as 2½p and 3½p show more detailed subdivisions adapted to a local weight system. Te denomination of 2½ pennies agrees well with the value of a Carolingian penny. Te diferent weight groups have very uniform measurements that vary only a few hundredths of a gram from the respective target weights. Regarding target weights and measured weights, this system is afected in the same way as the other weight systems. Table 21:7. Weights assigned to the Gutnic mark system. Target weight: Weights

1p 0,708g 0,76 D?

2p 1,416g

1,39D?

2½p 1,77g 1,73-1,75 1,77 1,78 1,78

3p 2,124g 2,06 2,13 D?

3½p 2,478g 2,42 2,45 2,47

4½p 3,186g 3,15-3,2

5p 3,54g 3,69

Medieval Scandinavian/Swedish mark weight Te weights that appear to belong to the later Scandinavian/Swedish mark weight system also are close to the target weights for the whole and half pennies up to ½ örtug. Unfortunately, there are so few weights in these groups that this may appear to be weakly substantiated. At present, these may be used until there are better alternatives. Table 21:8. Weights assigned to the medieval Scandinavian/Swedish mark system. Target weight:

1p 1,098g 1,15

1½p 1,647g 1,65 1,68 1,62

2p 2,195g 2,2 2,25

2½p 2,745g 2,725

3p 3,292g 3,26

½ örtug 4,39g 4,31 D?

Dirham/Mitqual, the Islamic weight series Te last group of weights is adapted to the Islamic system, above all, to whole as well as fractions of the dirham. However, the majority of weights perhaps could be included in the Gutnic series. It is likely that this is primarily a chronological matter, but it also can be linked to an adaptation between the two systems. Did these weights come into existence before or after the breakthrough in contacts with the East in the late ninth century? For the time being, the fractions shown in Table 21:9 are viewed as part of the Islamic system with the intermediate subsidiary weights, the 1p, 2p, and 3p values, included in the Gutnic series. Otherwise, the discussion for this group is similar to that for the other groups.

220

½örtug 4,248g 4,13 4,17 4,07 D?V? 4,01 D?V?

Table 21:9. Weights assigned to the Islamic dirham/mitqual. Target weight:

¼Dh 0,71g 0,76 G? 0,71 G?

½Dh 1,41g 1,41 G? 1,39 G? 1,435

¾Dh 2,115g 2,06 2,13

1 Dh 2,82g 2,82 2,84 2,83 2,87 2,84 2,81

1Mq? 4,23g 4,28 S?

To conclude, the vast majority of weights belong to clearly determinable levels with several weights each in each of the four weight systems (Fig. 21:11). Other weights, although they lack direct equivalents, ft well into other levels in the systems. Te mixture of diferent weight systems (Fig. 21:12) at each site suggests that trade and contacts with the surrounding world were extensive, likely requiring an ability and knowledge to assess the weight of payment in diferent areas. Merchants appear to have had their own personal sets of weights that allowed them to trade in diferent areas. Tis is seen in the more complete weight sets in the Birka graves as well as in other contexts and areas of present-day Sweden (Example 2). Stratigraphic distribution Te distribution of the system-classifed cubo-octahedral weights across Birka's stratigraphy is shown in letter codes in stratigraphic diagram Fig. 21:13. One such weight, found in waste layer B428 in the northern passage, seems to suggest a date before AD 870. However, it likely was discarded together with later layers from inside the adjacent northern plot. Tis part of the northern passage was redug in places during the Viking Age and later disturbed by Hjalmar Stolpe’s trenches in the 1870s. Tus, the date of this weight is uncertain. Weights belonging to the light Viking Age mark system begin to appear at the transition between phases B5 and B6 around AD 870. Tey dominated during phases B6 and B7 until around AD 930. During this period, only a few weight fnds can be linked to the Gutnic system or the dirham. Tese appear in layers in the plots that often originate from later levels in the stratigraphic sequence. When discarded in the passage, the stratigraphic sequence is disturbed and reversed: material from earlier layers are dumped on layers of later material. Gutnic and dirham weights begin to appear in the plots during phase B7, reaching a maximum during phases B8 and B9. Most of the weights linked to the Gutnic and dirham systems were found in the southern plot, which also otherwise showed evidence of a strong connection to trade with the East (e.g. Ambrosiani & Gustin 2015). Heavier ninth-century lead weights that belong to the later Scandinavian/Swedish system were found in the bronze caster’s workshop. Several tenth-century cubo-octahedral weights of lead bronze that also belong to this weight system were found in the northern plot and the northern passage, sub-area **8. Tese likely originate from the ploughed occupation layers inside the plots. Tus, weights linked to the dirham and the Scandinavian/ Swedish systems appear in the southern and northern plots, respectively. Tey may represent diferent activities in these two plots, but the evidence for a reliable interpretation is meagre.

221

V mark-weight 1p 1½p 2p 4,5

2½p

G mark-weight 1p 2p 2½p

3p

4

4

3,5

3,5

3

3

2,5

2,5

2

2

1,5

1,5

1

1

0,5

0,5

0

0

S mark-weight 1p 1½ 2p

2½p

Dirham/mitqual ¼D ½D ¾D

3p ½örtug

4,5 4

4 3,5

3

3

2,5

2,5

2

2

1,5

1,5

1

1

0,5

0,5

0

0

Fig. 21:12

4,5 4 3,5

1D

1M

4,5

3,5

5

3p 3½p 4½p 5p ½ört

4,5

V

G

S

D

Fig. 21:11. Cubo-octahedral weights from the Black Earth excavations 1990–1995 with calculated weights at a density of 8.7 and according to weight system. For abbreviations of weight system designations, see Table 21:1.

3 2,5 2 1,5 1 0,5 0

222

Fig. 21:12. Te four charts in the previous fgure combined.

Schema Fig. 21:13 Kubooktaeder, brons i Sv J 90-95 fördelning på viktsystem BS10: **S3-2 **S1 **9 **6 Plow B94*b B94*a DD CVVGGS B93* B92*b B92*a B91*b VVGD VVG B91*a S B84* ■ B83*b-d VG VV■ ■ S B83*a GD ■ B82*b D B82*a S ■ B81*b B81*a B8*5b B8*5a B75*b B75*a D B74*b-d B74*a B73*b GV B73*a V■ B72*b G B72*a ■ B71* ■ B62* V V V B61* Refill B59* B58* VGGGGS B57*b-c B57*a B56 B55 B54 B53 B52 B51 B47 B46 B45 B44 B43 B42 B41 B32 B31 B27 B26 Fig. 21:13. Stratigraphic B25 diagram of the cubo- B24 octahedral weights from B23 B22 the Black Earth excavations B21 1990–1995, according to B11* B0 weight system. BS9: **7 **9 **6 **1 Legend:

Deposited on plot

V = Viking age

**5a

Redistributed in alleys

G = Gutnic

**5b

**4

**3

**8

S■ V V■

GDS■■ D

V G

D D

■ V

■

**2

**5

**4

**3

**8

Redistributed but stratigraphically locked

S = Scandinavian/Swedish

D = Dirham/Mitqual

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Several questions remain concerning the chronology of the lead weights. It is not likely that weights related to the dirham system could have been used at Birka before the last decades of the ninth century. Tis is in agreement with Heiko Steuer and, to some extent, Tye. Before this, however, many lead weights are in use. Sperber attributed these weights to the Islamic systems. Lead weights are found throughout the entire stratigraphic sequence from phases B1–B5. In what way are these weights actually linked to the diferent weight systems? A control of the relationship between these systems and the approximately 200 lead weights is carried out in Example 5.

Example 5: Lead weights from the 1990–1995 excavations in the Black Earth Introduction According to the Birka Project's database, 200 objects are interpreted and registered as lead weights. However, these must be assessed critically to identify which weights fulfll the qualitative requirements for metrological analysis. Several weights are irregular in shape which excludes them from the following calculations. Sperber evaluated about 155 weights of diferent quality based on occular observations of the efects of corrosion (Sperber 2004 [BS6], 72 f.). Another 15–17 weights with measured values of between 5.0 and 8.5 g are not possible to identify in Sperber’s lists. Tese are interesting in interpreting connections with possible weight systems (see below). About 20 weights are described in the database as damaged. It is questionable whether they are suitable for calculations. Sperber, however, has measured the densities of some. Tese are given a value for adjusted density also here, although they likely fall below their expected target weights. Terefore, they probably are difcult to associate with a particular target weight. Tey are not included in the following diagrams because their reconstructed weights renders them unsuitable for analysis. A total of 119 weights can be used in a metrological analysis, 16 of which weigh more than 5 g (Figs. 21:14 a–b lighter, and 21:15 a–b heavier weights). Isotope analysis Twenty-fve lead weights from the 1990–1995 excavations have undergone isotope analysis, performed by Sophie Stos-Gale, to ascertain the provenance of the lead (Stos-Gale 2004). Each natural occurrence has a specifc combination of isotopes, which make the deposits possible to identify. According to Stos-Gale, two thirds of the analyzed weights are made with lead from Derbyshire; a couple of weights are made with lead from the Leadhills in Scotland; and one weight is made with lead from the Mendips in Wales. Only fve weights can be traced to the European continent: one from the Balkans; one from Freiberg in Germany; and three from the Rhineland, probably Eifel or Harzgebirge, in western Germany. Several years after this study, and based on many samples, Merkel points out that the lead deposits in Derbyshire in the West and the Eifel area in the Rhineland in the East actually compose peripheries of an overlaping central deposit (Merkel 2016, 229– 230). Terefore, on this basis, the concentration of the Birka samples possibly may derive

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Fig. 21:14a

Fig. 21:14b

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