Sulfide Mineralogy and Geochemistry 9781501509490, 9780939950737

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REVIEWS IN MINERALOGY AND GEOCHEMISTRY Volume 61

2006

SULFIDE MINERALOGY AND GEOCHEMISTRY EDITOR

David J. Vaughan University of Manchester Manchester, United Kingdom C O V E R P H O T O G R A P H : Cubo-octahedral crystals of galena (PbS) with calcite (white) on brown crystalline siderite, Neudorf, Harz, Germany. Copyright the Natural History Museum (London); reproduced with permission.

Series Editor: Jodi J. Rosso GEOCHEMICAL SOCIETY MINERALOGICAL SOCIETY OF AMERICA

COPYRIGHT 2006 M I N E R A L O G I C A L S O C I E T Y OF A M E R I C A The appearance of the code at the bottom of the first page of each chapter in this volume indicates the copyright owner's consent that copies of the article can be made for personal use or internal use or for the personal use or internal use of specific clients, provided the original publication is cited. The consent is given on the condition, however, that the copier pay the stated per-copy fee through the Copyright Clearance Center, Inc. for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to other types of copying for general distribution, for advertising or promotional purposes, for creating new collective works, or for resale. For permission to reprint entire articles in these cases and the like, consult the Administrator of the Mineralogical Society of America as to the royalty due to the Society.

REVIEWS IN AND

MINERALOGY

GEOCHEMISTRY

( Formerly:

REVIEWS IN MINERALOGY )

ISSN 1529-6466

Volume 61

Sulfide Mineralogy and Geochemistry ISBN 0-939950-73-1

Additional copies of this volume as well as others in this series may be obtained at moderate cost from: THE M I N E R A L O G I C A L S O C I E T Y OF A M E R I C A 3 6 3 5 CONCORDE PARKWAY, SUITE 5 0 0 CHANTILLY, VIRGINIA, 2 0 1 5 1 - 1 1 2 5 , U . S . A . WWW.MINSOCAM.ORG

SULFIDE MINERALOGY and GEOCHEMISTRY 61

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FROM THE SERIES EDITOR When the first Sulfide volume was published in 1974, by the Mineralogical Society of America with Paul Ribbe as the Editor, little did we forsee what exciting adventure was ahead. But here we are, 33 years and 60 RiMG volumes later. Publishing technologies may have changed (no more typewriters or ditto's), the faces of the scientists (and editors) have grown older (or changed all together), but our enthusiasm for mineralogy and geochemistry hasn't. Let's hope that this present volume on Sulfide Mineralogy and Geochemistry will usher in the next 60 RiMG volumes with as much impact as the first did! Many thanks to David Vaughan for his dedication to this volume. He was always available when questions arose, was faithful to adhere to our deadlines, and gracefully encouraged his authors to do the same. It was a delight to work with him. Supplemental material and errata (if any) can be found at the MSA website www. minsocam. org. Todi T. P-osso, Series Editor West Richland, Washington June 2006

PREFACE The metal sulfides have played an important role in mineralogy and geochemistry since these disciplines first emerged and, for reasons detailed in the first chapter, have achieved an even greater importance in both fundamental and applied mineral sciences in recent years. It is no surprise that Volume 1 in the series, of which this book is Volume 61, was devoted to "Sulfide Mineralogy." For some years there has been the need for an updated volume covering the subject areas of Volume 1 and addressing the new areas which have developed since its publication in 1974. I am grateful to Paul Ribbe, former RiMG Series Editor, for persistently encouraging me to undertake this new volume on sulfides. I am also grateful to my longstanding collaborator Jim Craig for facilitating acquisition of the copyright of our 1978 book "Mineral Chemistry of Metal Sulfides" and for his encouragement in this project. Liane Benning, Jim Craig, Jeff Grossman, Richard Harrison, Michael Hochella, Jon Lloyd, Dave Polya, Wayne Nesbitt, Pat Shanks, Michele Warren and Jack Zussman have all kindly given of their time to review draft versions of the chapters in this volume. I am also grateful to Jodi Rosso, RiMG Series Editor, for her heroic efforts in bringing this book to completion, and to our contributors for all their hard work. David J. Vaughan University of Manchester June 2006

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TABLE OF CONTENTS 1

Sulfide Mineralogy and Geochemistry: Introduction and Overview David J. Vaughan

BACKGROUND: WHY STUDY SULFIDES? PREVIOUS WORK: THE RELEVANT LITERATURE 1 III! l ' R I S I M 11 XI: SCOPE AND CONTENT REFERENCES

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1 2 3 5

Crystal Structures of Sulfides and other Chalcogenides Emit Makovicky

INTRODUCTION Crystal chemical concepts Structural classification PRINCIPLES OF THE DESCRIPTION AND CLASSIFICATION OF CRYSTAL STRUCTURES RELEVANT TO SULFIDES: A BRIEF OUTLINE Non-modular categories of similarity Modular categories of structural similarity CHALCOGENIDES WITH PRONOUNCED ONE-DIMENSIONAL BUILDING UNITS Fibrous sulfides with chains of edge-sharing FeS 4 tetrahedra Other fibrous sulfides STRUCTURE TYPES COMPOSED OF LAYERS: CHALCOGENIDE LAYERS WITH M:S =1:1 Mackinawite and related families Other M:S=1:1 layer types STRUCTURES COMPOSED OF SESQUICHALCOGENIDE LAYERS STRUCTURES COMPOSED OF DICHALCOGENIDE LAYERS LAYER-LIKE STRUCTURES WITH TWO TYPES OF CHALCOGENIDE LAYERS Cannizzarite and related structures Derivatives of cannizzarite: combinations of accretion with variable-fit v

7 7 9 12 12 12 16 16 19 19 19 22 25 28 31 31 32

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Selected synthetic and natural chalcogenides with layer-misfit structures Cylindrite family: a doubly-noncommensurate example STRUCTURES Wi l li 31) I RAMI WORKS Adamantane structures Structures based on the sphalerite stacking principle Structures based on the wurtzite stacking principle Adamantane structures with additional, interstitial tetrahedra The problem of interstitial cations in hep and related stackings Defect adamantane structures and more complicated cases Summary of cation-cluster configurations Tetrahedrite-tennantite Structures with anion vacancies Structures with tetrahedral clusters Monosulfides with octahedral cations: ccp vs. hep stacking of anions Thiospinels Disulfides, sulfarsenides and their analogs CHANNEL AND CAGE STRUCTURES CATION S|'| ( II l( STRUCTURES Mercury sulfides Nickel sulfides Sulfides of palladium and platinum IONIC CONDUCTORS AND THE CHALCOGENIDES OF Cu AND Ag I ONI! ELECTRON PAIR COMPOUNDS Molecular arsenic sulfides Ribbon-like arrangements The bismuthinite-aikinite series of sulfosalts Layer-like structures LARGE St ! I OSAI T I AMII II S General features Lillianite homologous series PAVONITE HOMOLOGOUS SERIES CUPROBISMUTITE HOMOLOGOUS SERIES Rod-based sulfosalts Case study: dadsonite Other sulfosalt families ACKNOWLEDGMENTS REFERENCES

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35 38 40 40 44 45 45 50 52 52 53 55 55 60 63 65 69 69 69 70 72 77 84 84 87 88 90 90 90 92 94 95 97 99 105 107 107

Electrical and Magnetic Properties of Sulfides Carolyn I. Pearce, Richard A.D. Pattrick, David J. Vaughan

INTRODUCTION THEORY AND MEASUREMENT OF ELECTRICAL AND MAGNETIC PROPERTIES Electrical properties Measurement of electrical properties vi

127 127 127 128

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Magnetic properties Measurement of magnetic properties ELECTRICAL AND MAGNETIC PROPERTIES OF METAL SULFIDES Metal sulfides of sphalerite and wurtzite (ZnS) structure-type Sulfides of pyrite (FeS2) and related structure-types Sulfides with halite (NaCl) structures Sulfides with niccolite (NiAs)-based structures Mackinawite, smythite, greigite and other thiospinels PROPERTIES OF SULFIDE NANOPARTICLES Synthesis of sulfide nanoparticles Case study: pure and transition metal (TM) ion doped ZnS Sulfide nanoparticles in the environment APPLICATIONS Electronics Paleomagnetic investigations Beneficiation of sulfide ores CONCLUDING COMMENTS ACKNOWLEDGMENTS REFERENCES

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133 139 145 148 150 156 157 163 164 166 166 169 169 169 170 171 172 172 172

Spectroscopic Studies of Sulfides Paul L. Wincott and David J. Vaughan

INTRODUCTION ELECTRONIC (OPTICAL) ABSORPTION AND REFLECTANCE SPECTRA Spectra of sphalerite and wurtzite-type sulfides Spectra of pyrite-type disulfides Spectra of the layer sulfides (MoS2) INFRARED AND RAMAN SPECTRA X-RAY AND ELECTRON EMISSION SPECTROSCOPIES X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) X-ray emission spectroscopy Applications to non-transition metal monosulfides: PbS, ZnS, CdS and HgS Applications to the transition metal sulfides: FeS, F e ^ S , CuS, Cu^S, Ag2S, CuFeS 2 and related phases Application to the disulfides: FeS 2 , MoS 2 X-RAY ABSORPTION SPECTROSCOPIES Extended X-ray absorption fine structure spectroscopy (EXAFS) and X-ray absorption near-edge structure spectroscopy (XANES) Applications to binary metal sulfides: PbS, ZnS, CdS, HgS, CaS, MgS, MnS, FeS, CoS, NiS and CuS Applications to disulfides: pyrite group (MS 2 where M = Fe, Co, Ni) and MoS 2 Ternary and complex sulfides: chalcopyrite, tetrahedrite group MOSSBAUER STUDIES Pyrite, marcasite, arsenopyrite and related minerals vii

181 182 184 186 187 188 191 192 194 195 198 200 201 201 204 206 206 208 210

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Thiospinel minerals Mackinawite and pentlandite Sphalerite and wurtzite-type sulfide minerals Troilite and pyrrhotite High-pressure Mossbauer spectroscopy of sulfides OTHER SPECTROSCOPIC TECHNIQUES CONCLUDING REMARKS ACKNOWLEDGMENTS REFERENCES

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211 214 215 217 218 219 221 221 221

Chemical Bonding in Sulfide Minerals David J. Vaughan, Kevin M. Rosso

INTRODUCTION 231 IONIC AND COVALENT BONDS 231 LIGAND FIELD THEORY 232 QUALITATIVE MOLECULAR ORBITAL (MO) AND BAND MODELS 234 QUANTITATIVE APPROACHES: ATOMISTIC COMPUTATION 237 QUANTITATIVE APPROACHES: ELECTRONIC STRUCTURE CALCULATIONS .... 23 8 CHEMICAL BONDING AND ELECTRONIC STRUCTURE IN SOME MAJOR SULFIDE MINERALS AND GROUPS 241 Generalities 241 Galena (PbS) 243 Sphalerite and related sulfides (ZnS, Zn(Fe)S, CdS, HgS, CuFeS 2 ) 245 Transition metal monosulfides (FeS, F e ^ S , CoS, NiS) 248 Pyrite and the related disulfides (FeS2, CoS2, NiS2, CuS2, FeAsS, FeAs 2 ) 252 Other (including complex) sulfides (pentlandites and metal-rich sulfides, thiospinels, layer structure sulfides, tetrahedrites) 255 CONCLUDING REMARKS 258 ACKNOWLEDGMENTS 259 REFERENCES 259

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Thermochemistry of Sulfide Mineral Solutions Richard O. Sack, Denton S. Ebel

INTRODUCTION SULFIDE THERMOCHEMISTRY Basic concepts Dimensionality of systems Mineral stability and criteria for equilibrium Experimental methods in sulfide research SULFIDE SYSTEMS IN METEORITES Fe-S viii

265 266 266 271 272 273 280 282

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Zn-Fe-S Ag2S-Cu2S-Sb2S3-As2S3 Sulfosalts (Ag2S-Cu2S)-Sb2S3-As2S3 Ag2S-Cu2S As-Sb exchange THE SYSTEM Ag2S-Cu2S-ZnS-FeS-Sb2S3-As2S3 Fahlore thermochemistry Thermochemical database Bi S; AND PbS-BEARING SYSTEMS The Bi2S3-Sb2S3-AgBiS2-AgSbS2 quadrilateral The quaternary system Ag2S-PbS-Sb2S3-Bi2S3 The system Ag 2 S-Cu 2 S-ZnS-FeS-PbS-Sb 2 S 3 -As 2 S 3 ACKNOWLEDGMENTS REFERENCES APPENDICES

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290 299 300 307 310 311 313 320 323 324 328 333 336 337 349

Phase Equilibria at High Temperatures Michael E. Fleet

INTRODUCTION Fe, Co AND Ni SULFIDES AND THEIR MUTUAL SOLID SOLUTIONS Monosulfides of Fe, Co and Ni Fe-S phase relations Ni-S phase relations The system Fe-Co-S Ternary phase relations in the system Fe-Ni-S Cu-S, Cil 1 c S AND Cu-Fe-Zn-S SYSTEMS Phase relations in the system Cu-S Phase relations in the ternary system Cu-Fe-S Sulfur fugacity in ternary Cu-Fe-S system Quaternary System Cu-Fe-Zn-S ZnS AND Fe-Zn-S SYSTEM ZnS Ternary Fe-Zn-S system and geobarometry Calculated phase relations HALITE STRUCTURE MONOSULFIDES Electronic structure and magnetism Phase relations ACKNOWLEDGMENTS REFERENCES

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365 365 370 374 380 381 382 383 385 388 392 392 395 395 396 401 403 403 404 405 405

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Metal Sulfide Complexes and Clusters David Rickard, George W. Luther, III

INTRODUCTION Background Metals considered in this chapter Lewis acids and bases Hard A and soft B metals Complexes and clusters Coordination numbers and symmetries Equilibrium constants of complexes METHODS FOR MEASUREMENT OF METAL SULFIDE STABILITY CONSTANTS Theoretical approaches to the estimation of stability constants Experimental approaches to the measurement of metal sulfide stability constants METHODS USED TO DETERMINE THE MOLECULAR STRUCTURE AND COMPOSITION OF ( O M P I I X I S

421 421 423 424 425 426 427 428 430 432 434 442

Chemical synthesis of complexes LIGAND STABILITIES AND STRUCTURES Molecular structures of sulfide species in aqueous solutions S (-II) equilibria in aqueous solutions Polysulfide stabilities METAL SULFIDE COMPLEXES The first transition series: Cr, Mn, Fe, Co, Ni, Cu Molybdenum Silver and gold Zinc, cadmium and mercury Tin and lead Arsenic and antimony Selected metal sulfide complex stability constants KINETICS AND MECHANISMS OF METAL SULFIDE FORMATION Properties of metal aqua complexes Mechanisms of formation of metal sulfide complexes Metal isotopic evidence for metal sulfide complexes COMPLEXES, CLUSTERS AND MINERALS Zinc sulfide clusters Iron sulfide clusters The relationship between complexes, clusters and the solid phase ACKNOWLEDGMENTS REFERENCES

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443 444 444 446 448 450 450 461 462 466 472 474 478 483 483 485 489 489 491 493 494 495 496

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Sulfide Mineral Surfaces Kevin M. Rosso, David J. Vaughan

INTRODUCTION SURFACE PRINCIPLES Surface energy Atomic structure Electronic structure EXAMPLE SURFACES Crystallographic surfaces Fracture surfaces FUTURE OUTLOOK ACKNOWLEDGMENTS REFERENCES

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505 506 506 507 512 516 516 542 548 549 550

Reactivity of Sulfide Mineral Surfaces Kevin M. Rosso, David J. Vaughan

INTRODUCTION ELEMENTARY ADSORPTION/OXIDATION REACTIONS Galena Pyrite AIR/AQUEOUS OXIDATION Galena Pyrite Pyrrhotite Chalcopyrite Arsenopyrite CATALYSIS Laurite Molybdenite FUNCTIONALIZATION AND SELF-ASSEMBLY Collector molecule adsorption METAL ION UPTAKE Galena Pyrite Pyrrhotite and troilite Mackinawite Sphalerite and wurtzite FUTURE OUTLOOK ACKNOWLEDGMENTS REFERENCES

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557 558 558 562 565 565 567 571 571 573 576 576 578 580 581 592 592 593 595 596 599 599 600 600

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Sulfide Mineral Precipitation from Hydrothermal Fluids Mark H. Reed, James Palandri

INTRODUCTION Calculation method Data sources SULFIDE MINERAL SOLUBILITY: BASIC CONTROLS SULFIDE MINERAL NUMERICAL EXPERIMENTS Chloride addition (Run 1) Simple dilution (Run 2) Silicate-buffered dilution (Run 3) Temperature change (Run 4) pH change (Runs 5, 6, 7, 8) Simultaneous dilution and cooling by cold water mixing (Run 9) Oxidation and reduction of a sulfide-oxide system (Run 10) ( ON( I 1SION REFERENCES

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609 609 610 610 611 613 614 618 619 619 625 627 629 630

Sulfur Isotope Geochemistry of Sulfide Minerals Robert R. Seal, II

INTRODUCTION FUNDAMENTAL ASPECTS OF SULFUR ISOTOPE GEOCHEMISTRY ANALYTICAL METHODS REFERENCE RI SI RYOIRS FACTORS THAT CONTROL SULFUR ISOTOPE FRACTIONATION EQUILIBRIUM FRACTIONATION FACTORS Experimentally determined fractionation factors Geo thermometry PROCESSES THAT RESULT IN STABLE ISOTOPIC VARIATIONS OF SULFUR Mass-dependent fractionation processes Mass-independent fractionation processes GEOCHEMICAL ENVIRONMENTS Meteorites Marine sediments Coal Mantle and igneous rocks Magmatic sulfide deposits Porphyry and epithermal deposits Seafloor hydrothermal systems Mississippi Valley-type deposits SUMMARY ACKNOWLEDGMENTS REFERENCES xii

633 634 636 637 638 638 639 641 642 642 648 650 650 651 653 655 657 658 662 666 668 669 670

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Sulfides in Biosystems Mihaly Posfai, Rafal E. Dunin-Borkowski

INTRODUCTION BIOLOGICAL FUNCTION AND MINERAL PROPERTIES: CONTROLLED MINERALIZATION OF IRON SULFIDES Biologically controlled mineralization in magnetotactic bacteria Sulfide-producing magnetotactic bacteria Structures and compositions of iron sulfide magnetosomes Magnetic sensing with sulfide magnetosomes Mechanical protection: iron sulfides on the foot of a deep-sea snail BIOLOGICALLY INDUCED FORMATION OF SULFIDE MINERALS Microbial sulfate and metal reduction The role of biological surfaces in mineral nucleation Iron sulfides in marine sediments Biogenic zinc sulfides: from mine-water to deep-sea vents BIOLOGICALLY MEDIATED DISSOLUTION OF SULFIDE MINERALS Acid mine drainage Microbial degradation of sulfides in marine environments PRACTICAL APPLICATIONS OF INTERACTIONS BETWEEN ORGANISMS AND SULFIDES Biomimetic materials synthesis Bioremediation Bioleaching of metals IRON SULFIDES AND THE ORIGIN OF LIFE CONCLUDING THOUGHTS ACKNOWLEDGMENTS REFERENCES

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679 680 681 682 684 685 689 692 692 693 693 699 701 701 703 704 704 705 705 706 707 708 708

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Reviews in Mineralogy & Geochemistry Vol. 61, pp. 1-5, 2006 Copyright © Mineralogical Society of America

Sulfide Mineralogy and Geochemistry: Introduction and Overview David J. Vaughan School of Earth, Atmospheric and Environmental Sciences and Williamson Research Centre for Molecular Environmental Science University of Manchester Manchester, United Kingdom e-mail:

[email protected]

BACKGROUND: WHY STUDY SULFIDES? The metal sulfides are the raw materials for most of the world supplies of non-ferrous metals and, therefore, can be considered the most important group of ore minerals. Although there are several hundred known sulfide minerals, only a half dozen of them are sufficiently abundant as to be regarded as "rock-forming minerals" (pyrite, pyrrhotite, galena, sphalerite, chalcopyrite and chalcocite; see Bowles and Vaughan 2006). These mostly occur as accessory minerals in certain major rock types, with pyrite being by far the most important volumetrically. It is also important to note that the synthetic analogs of certain sulfide minerals are of interest to physicists and materials scientists because of their properties (electrical, magnetic, optical) and have found uses in various electronic or opto-electronic devices. Recently, this interest has been directed towards the use in such devices of metal sulfide thin films and of sulfide nanoparticles, topics touched upon in Chapter 3 but not discussed in detail in this volume (but see, for example, Fuhs and Klenk 1998; Bernede et al. 1999; Trindade et al. 2001). The importance of sulfide minerals in ores has long been, and continues to be, a major reason for the interest of mineralogists and geochemists in these materials. Determining the fundamental chemistry of sulfides is key to understanding their conditions of formation and, hence, the geological processes by which certain ore deposits have formed. This, in turn, may inform the strategies used in exploration for such deposits and their subsequent exploitation. In this context, knowledge of structures, stabilities, phase relations and transformations, together with the relevant thermodynamic and kinetic data, is critical. As with many geochemical systems, much can also be learned from isotopic studies. The practical contributions of mineralogists and geochemists to sulfide studies extend beyond areas related to geological applications. The mining of sulfide ores, to satisfy ever increasing world demand for metals, now involves extracting very large volumes of rock that contains a few percent at most (and commonly less than one percent) of the metal being mined. This is true of relatively low value metals such as copper; for the precious metals commonly occurring as sulfides, or associated with them, the mineable concentrations {grades) are very much lower. The "as-mined" ores therefore require extensive processing in order to produce a concentrate with a much higher percentage content of the metal being extracted. Such mineral processing (beneficiation) involves crushing and grinding of the ores to a very fine grain size in order to liberate the valuable metal-bearing (sulfide) minerals which can then be concentrated. In some cases, the metalliferous (sulfide) minerals may have specific electrical or magnetic properties that can be exploited to enable separation and, hence, concentration. More commonly, froth flotation is used, whereby the surfaces of particles of a particular mineral phase are rendered water repellent by the addition of chemical reagents and hence are attracted 1529-6466/06/0061-0001 $05.00

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to air bubbles pulsed through a mineral particle-water-reagent pulp. An understanding of the surface chemistry and surface reactivity of sulfide minerals is central to this major industrial process and, of course, knowledge of electrical and magnetic properties is very important in cases where those particular properties can be utilized. In the years since the publication of the first ever "Reviews in Mineralogy" volume (at that time called MSA "Short Course Notes") which was entitled "Sulfide Mineralogy" (Ribbe 1974), sulfides have become a focus of research interest for reasons centering on at least two other areas in addition to their key role in ore deposit studies and mineral processing technology. It is in these two new areas that much of the research on sulfides has been concentrated in recent years. The first of these areas relates to the capacity of sulfides to react with natural waters and acidify them; the resulting Acid Rock Drainage (ARD), or Acid Mine Drainage (AMD) where the sulfides are the waste products of mining, has the capacity to damage or destroy vegetation, fish and other aquatic life forms. These acid waters may also accelerate the dissolution of associated minerals containing potentially toxic elements (e.g., As, Pb, Cd, Hg, etc.) and these may, in turn, cause environmental damage. The much greater public awareness of the need to prevent or control AMD and toxic metal pollution has led to regulation and legislation in many parts of the world, and to the funding of research programs aimed at a greater understanding of the factors controlling the breakdown of sulfide minerals. Amongst general references dealing with these topics, which are all part of the emerging field of "Environmental Mineralogy," are the texts of Jambor and Blowes (1994), Vaughan and Wogelius (2000), Cotter-Howells et al. (2000) and Jambor et al. (2003). The second reason for even greater research interest in sulfide minerals arose initially from the discoveries of active hydrothermal systems in the deep oceans. The presence of life forms that have chemical rather than photosynthetic metabolisms, and that occur in association with newly-forming sulfides, has encouraged research on the potential of sulfide surfaces in catalyzing the reactions leading to assembling of the complex molecules needed for life on Earth (see, for example, reviews by Vaughan and Lennie 1991; Russell and Hall 1997; Hazen 2005). These developments have been associated with a great upsurge of interest in the interactions between microbes and minerals, and in the role that minerals can play in biological systems. In the rapidly growing field of geomicrobiology, metal sulfides are of major interest. This interest is related to a variety of processes including, for example, those where bacteria interact with sulfides as part of their metabolic activity and cause chemical changes such as oxidation or reduction, or those in which biogenic sulfide minerals perform a specific function, such as that of navigation in magnetotactic bacteria. The development of research in areas such as geomicrobiology and environmental mineralogy and geochemistry, is also leading to a greater appreciation of the role of sulfides (particularly the iron sulfides) in the geochemical cycling of the elements at or near the surface of the Earth. For example, the iron sulfides precipitated in the reducing environments beneath the surface of modern sediments in many estuarine areas may play a key role in the trapping of toxic metals and other pollutants. In our understanding of "Earth Systems," geochemical processes involving metal sulfides are an important part of the story. Thus, interest in sulfide mineralogy and geochemistry has never been greater, given the continuing importance of the long established applications in ore geology and mineral technology, and the new fields of application related to geomicrobiology, the environment, and "Earth Systems."

PREVIOUS WORK: THE RELEVANT LITERATURE The literature on sulfide mineralogy and geochemistry is spread across a very wide range of journals and related publications. This includes not only journals of mineralogy

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and geochemistry but also of crystallography, spectroscopy, materials science, pure and applied chemistry and physics, surface science, mineral technology and, more recently, of biogeochemistry and the environmental sciences. Textbooks devoted specifically to sulfide mineralogy are Ribbe (1974), Vaughan and Craig (1978), and Kostov and Mincheeva-Stefanova (1981). All of these volumes are now out of print, although sometimes still available through library copies. The text by Vaughan and Craig (1978) has recently been made freely available on the internet (http://www.manchester.ac.uk/ digitallibrary/books/vaughan). As well as these books dealing with sulfide minerals in general, Mills (1974) provides a wealth of thermodynamic data, and Shuey (1976) reviews the electrical properties of many common sulfides. The books by Barnes (1979,1997), Garrels and Christ (1965) and Stanton (1972) also contain much of relevance to those interested in the geochemical and petrological aspects of sulfide studies. As all but a handful of the sulfide minerals are opaque to visible light, the standard method used for initial identification (in a manner analogous to study of a petrographic thin section) and for the characterization of textural and paragenetic relationships, is examination in polished section using the reflected light microscope (commonly known as ore microscopy). Here, the texts by Ramdohr (1969, 1980), Uytenbogaart and Burke (1971), Craig and Vaughan (1994), Jambor and Vaughan (1990) and Cabri and Vaughan (1998) all present much information on the ore microscopy and ore petrography of sulfides. Routine ore microscopy involves qualitative observation of a range of properties, and this is often sufficient for the trained observer to identify phases (with techniques such as X-ray powder diffraction and electron probe microanalysis being used to provide confirmation and more detailed characterization). Certain key properties observed qualitatively using the ore microscope can also be measured using a suitably equipped microscope. Quantitative ore microscopy data (reflectance, quantitative color values, indentation microhardness values) for sulfides are provided by Criddle and Stanley (1993).

THE PRESENT TEXT: SCOPE AND CONTENT The main objective of the present text is to provide an up-to-date review of sulfide mineralogy and geochemistry, chiefly covering the areas previously dealt with in the books by Ribbe (1974) and by Vaughan and Craig (1978). The emphasis is, therefore, on such topics as crystal structure and classification, electrical and magnetic properties, spectroscopic studies, chemical bonding, high and low temperature phase relations, thermochemistry, and stable isotope systematics. In the context of this book, emphasis is on metal sulfides sensu stricto where only the compounds of sulfur with one or more metals are considered. Where it is appropriate for comparison, there is brief discussion of the selenide or telluride analogs of the metal sulfides. When discussing crystal structures and structural relationships, the sulfosalt minerals as well as the sulfides are considered in some detail (see Chapter 2; also for definition of the term "sulfosalt"). However, in other chapters there is only limited discussion of sulfosalts, in part because there is little information available beyond knowledge of chemical composition and crystal structure. Given the dramatic developments in areas of research that were virtually non-existent at the time of the earlier reviews, major sections have been added here on sulfide mineral surface chemistry and reactivity, formation and transformation of metal-sulfur clusters and nanoparticles, modeling of hydrothermal precipitation, and on sulfides in biosystems. However, it should be emphasized that the growth in the literature on certain aspects of sulfide mineralogy over the past 20 years or so has been such that comprehensive coverage is not possible in a single volume. Thus, the general area of "sulfides in biosystems" is probably worthy of a volume in itself, and "environmental sulfide geochemistry" (including topics such

4

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as oxidative breakdown of sulfides) is another area where far more could have been written. In selecting areas for detailed coverage in this volume, we have been mindful of the existence of other relatively recent review volumes, including those in the RiMG series. So, for example, readers looking for more information on mineral-microbe interactions are referred to Banfield and Nealson (1997), or on nanoparticles to Banfield and Navrotsky (2001). It has also been our intention not to cover any aspects of the natural occurrence, textural or paragenetic relationships involving sulfides, given the coverage already provided by Ramdohr (1969, 1980) and by Craig and Vaughan (1994), in particular. This is published information that, although it may be supplemented by new observations, is likely to remain useful for a long period and largely not be superceded by later work. In the following chapters, the crystal structures, electrical and magnetic properties, spectroscopic studies, chemical bonding, thermochemistry, phase relations, solution chemistry, surface structure and chemistry, hydrothermal precipitation processes, sulfur isotope geochemistry and geobiology of metal sulfides are reviewed. Makovicky (Chapter 2) discusses the crystal structures and structural classification of sulfides and other chalcogenides (including the sulfosalts) in terms of the relationships between structural units. This very comprehensive survey, using a rather different and complementary approach to that used in previous review volumes, shows the great diversity of sulfide structures and the wealth of materials that remain to be characterized in detail. These materials include rare minerals, and synthetic sulfides that may represent as yet undescribed minerals. Pearce, Pattrick and Vaughan (Chapter 3) review the electrical and magnetic properties of sulfides, discussing the importance of this aspect of the sulfides to any understanding of their electronic structures (chemical bonding) and to applications ranging from geophysical prospecting and mineral extraction to geomagnetic and palaeomagnetic studies. Rapidly developing new areas of interest discussed include studies of the distinctive properties of sulfide nanoparticles. Wincott and Vaughan (Chapter 4) then outline the spectroscopic methods employed to study the crystal chemistry and electronic structures of sulfides. These range from UV-visible through infrared and Raman spectroscopies, to X-ray emission, photoemission and absorption, and to nuclear spectroscopies. Chemical bonding (electronic structure) in sulfides is the subject of the following chapter by Vaughan and Rosso (Chapter 5), a topic which draws on knowledge of electrical and magnetic properties and spectroscopic data as experimental input, as well as on a range of rapidly developing computational methods. Attention then turns to the thermochemistry of sulfides in a chapter by Sack and Ebel (Chapter 6) which is followed by discussion of phase equilibria at high temperatures in the review by Fleet (Chapter 7). Sulfides in aqueous systems, with emphasis on solution complexes and clusters, forms the subject matter of the chapter written by Rickard and Luther (Chapter 8). Sulfide mineral surfaces are the focus of the next two chapters, both by Rosso and Vaughan. The first of these chapters (Chapter 9) addresses characterization of the pristine sulfide surface, its structure and chemistry; the second (Chapter 10) concerns surface reactivity, including redox reactions, sorption phenomena, and the catalytic activity of sulfide surfaces. Reed and Palandri (Chapter 11) show in the next chapter how much can now be achieved in attempting to predict processes of sulfide precipitation in hydrothermal systems. The final chapters deal with two distinctive areas of sulfide mineralogy and geochemistry. Seal (Chapter 12) presents a comprehensive account of the theory and applications of sulfur isotope geochemistry; sulfur isotope fractionation can provide the key to understanding the natural processes of formation of sulfide deposits. In the final chapter, Posfai and Dunin-Borkowski (Chapter 13) review the rapidly developing area of sulfides in biosystems, discussing aspects of both sulfide mineral-microbe interactions and biomineralization processes involving sulfides. It is inherent in multi-author compilations such as this volume that some relevant topics have been given relatively little attention, or even omitted, and there is also occasional duplication of material between chapters. In effect the reader should view each of the chapters as a "stand alone" account, albeit complemented by the other chapters. It is hoped that readers

Introduction & Overview

5

will appreciate the perspectives offered by the authors in approaching their material from very different standpoints. Having said this, every effort has been made to provide adequate cross referencing between chapters. As noted above, no attempt has been made to review the more "petrological" aspects of sulfide research (natural occurrence, textural and paragenetic relationships of sulfides in rocks and ores). It had been hoped to include more discussion of certain topics, such as the formation and transformation of metal sulfide precipitates, but in this and a number of other areas, that will have to await a future volume. Our hope is that despite its shortcomings, which are entirely the responsibility of the volume editor, this book will be a fitting successor to the 1974 "Sulfide Mineralogy" volume, the book which launched the whole "Reviews in Mineralogy and Geochemistry" series.

REFERENCES Banfield JF, Navrotsky A (eds) (2001) Nanoparticles and the Environment. Rev Mineral Geochem, Vol. 44. Mineralogical Society of America Banfield JF, Nealson KH (eds) (1997) Geomicrobiology: Interactions between Microbes and Minerals. Rev Mineral Geochem, Vol. 35. Mineralogical Society of America Barnes HL (ed) (1979, 1997) Geochemistry of Hydrothermal Ore Deposits.(2 nd and 3 rd edition) WileyInterscience Bernede JC, Pouzet J, Gourmelon E, Hadouda H (1999) Recent studies on photovoltaic thin films of binary compounds. Synth Met 99:45-52 Bowles JFW, Vaughan DJ (2006) Oxides and Sulphides. Vol. 5A. Rock-Forming Minerals (Deer, Howie, Zussman) Geol Soc London Publication (in press) Cabri LJ, Vaughan DJ (1998) Modern Approaches to Ore and Environmental Mineralogy. Min Assoc Canada Short Course, Vol. 27, 421 pp. Cotter-Howells J, Campbell L, Batchelder M, Valsami-Jones E (eds) (2000) Environmental Mineralogy: Microbial Interactions, Anthropogenic Influences, Contaminated Land and Waste Management. Mineral Soc Monog 9 Craig JR, Vaughan DJ (1994) Ore Microscopy and Ore Petrography. (2nd edition) Wiley-Interscience Criddle AJ, Stanley CJ (eds) 1993) Quantitative Data File for Ore Minerals. Chapman and Hall Fuhs W, Klenk R (1998) Thin film solar cells. EUR 18656. World Conference on Photovoltaic Solar Energy Conversion 1:381-386 Garrels RM, Christ CL (1965) Solutions, Minerals and Equilibria. Harper and Row Hazen RM (ed) (2005) Genesis: Rocks, Minerals and the Geochemical Origin of Life. Elements 1:135-161 Jambor JL, Blowes DW (eds) (1994) The Environmental Geochemistry of Sulfide Minewastes. Mineral Assoc Canada Short Course Handbook, Vol. 22 Jambor JL, Vaughan DJ (eds) (1990) Advanced Microscopic Studies of Ore Minerals. Mineral Assoc Canada Short Course, Vol.17 Jambor JL, Blowes DW, Ritchie AIM (eds) (2003) Environmental Aspects of Minewastes. Mineral Assoc Canada Short Course, Vol. 31 Kostov I, Mincheeva-Stefanova J (1981) Sulphide Minerals: Crystal Chemistry, Parageneses and Systematics. Bulgarian Academy of Sciences Mills KC (1974) Thermodynamic Data for Inorganic Sulphides, Selenides and Tellurides. Butterworth Ramdohr P (1969, 1980) The Ore Minerals and their Intergrowths. (1 st and 2nd English Editions) Pergamon Ribbe PH (ed) (1974) Sulfide Mineralogy. Mineral Soc Am Short Course Notes. Vol. 1. Mineralogical Society of America Russell MJ, Hall A (1997). The emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and pH front. J Geol Soc Lond 154:377-402 Shuey RT (1975) Semiconducting Ore Minerals. Devel in Econ Geol. No.4, Elsevier Stanton RL (1972) Ore Petrology. McGraw Hill Trindade T, O'Brien P, Pickett NL (2001) Nanocrystalline semiconductors: synthesis properties, and perspectives. ChemMater 13:3843-3858 Uytenbogaart W, Burke EAJ (1971) Tables for Microscopic Identification of Ore Minerals. Elsevier Vaughan DJ, Craig JR (1978) Mineral Chemistry of Metal Sulfides. Cambridge Univ Press, Cambridge [freely available electronically at: http://www.manchester.ac.uk/digitallibrary/books/vaughan Vaughan DJ, Lennie AR (1991) The iron sulphide minerals: their chemistry and role in nature. Science Progr Edinburgh 75: 371-388 Vaughan DJ, Wogelius RA (2000) Environmental Mineralogy. Notes in Mineralogy Vol. 2. European Mineral Union

2

Reviews in Mineralogy & Geochemistry Vol. 61, pp. 7-125,2006 Copyright © Mineralogical Society of America

Crystal Structures of Sulfides and Other Chalcogenides Emil Makovicky Geological Institute University of Copenhagen 0ster Voldgade 10, DK1350 Copenhagen, e-mail:

Denmark

[email protected]

INTRODUCTION In this chapter, the crystal structures of sulfides and related chalcogenide compounds (involving Se, Te, As and Sb as well as S) are reviewed with emphasis on mineral phases but with some discussion of related synthetic compounds. Before presenting a systematic account of the principal families, relevant crystal chemical concepts are discussed, and structural classification schemes for these phases are reviewed. Crystal chemical concepts Chalcogenide ions. Chalcogens differ from oxygen by their moderate electronegativity. The Pauling electronegativity of oxygen is 3.44, whereas that of S is 2.58, Se 2.55, and Te 2.1 (Emsley 1994). The Shannon crystal radius of O 2 " is 1.40 A, that of S 2 " 1.70 A, Se2" 1.84 A, and Te 2- 2.07 A (Shannon 1981). We have estimated the radius of As 3 - as about 1.78 A, and that of Sb3~ as 1.89 A, based on the structures of selected sulfide-pnictides. The difference in polarizability of chalcogens and oxygen is of great structural importance. The electric polarizability (i.e., the value expressing the displacement of the electron cloud relative to the nucleus) is 3.88 x 10"24 cm 3 for O2", but it is 10.2 x 10"24 cm 3 for S2", 10.5 x 10"24 cm 3 for Se 2- , and 14.0 x 10~24 cm 3 for Te 2- (Pauling 1927). The polarizability values can also be interpreted as expressing covalency trends of anion-cation bonds and anion-anion interactions in the structure. The difference between oxygen and chalcogens leads to differences in crystal chemistry of oxides and chalcogenides for nearly all element combinations, exceptions being very few. Structural features of certain chalcogenide categories are in common with hydroxides, which have low-charge and polarizable OH~ groups; this is true especially for layer-like structures. There are greater similarities between the above values for S and Se, and a more pronounced difference for Te. However, already the differences between the behaviour of S and Se, and presumably also the possibilities which the larger radius of Se offers for certain cation-cation distances in selenides, lead to important differences between phase diagrams of sulfides and selenides. With the notable exception of chalcogenides of typical non-metals, a fundamental crystalchemical division of chalcogenide structures can be based on the difference in electronegativity and bonding schemes between "cations" and "anions," and on Pearson's valence rule, UN = 8,

where S =

ne-ba-btC

In this expression, ne is the total number of valence electrons, ba the number of electrons involved in anion-anion bonds, and bc number of electrons involved in cation-cation bonds plus those left unshared on cations (i.e., constituting lone electron pairs). In polyanionic 1529-6466/06/0061-0002$ 15.00

DOI: 10.2138/rmg.2006.61.2

8

Makovicky

compounds, nJN< 8, in normal-valence compounds, nJN= 8, and in polycationic compounds, nJN > 8. As, Sb, and Bi may play either the role of an anion or that of a cation; details are in the section on structures with dichalcogenide groups X2. Cation-cation interactions may affect the M:X ratio as, e.g., in pentlandite (M9S8), but a range of weaker, although obvious cationcation interactions occur, especially in the chalcogenides of Cu and Ag, which do not alter their stoichiometry. Typically, the interaction distances in these compounds exceed those in a metal; see discussion by Chevrel (1992). Packing of anions. Another fundamental crystal-chemical principle relevant to the chalcogenides is that of "close packing of anions" (eutaxy). This is an arrangement in which the shortest distances between pairs of anions are as large as possible (O'Keeffe and Hyde 1996). The result, however, is the densest packing of atoms, corresponding to that seen in metals. To the cubic close packing (ccp) and the hexagonal close packing (hep) of anions, and their numerous combinations (O'Keeffe and Hyde 1996), is added a body-centered close packing, which has a lesser space-filling efficiency. It is generated, for example, by the steric requirements of silver cations in Ag 2 X, especially at elevated temperatures. The third most efficient mode of packing, the icosahedral configuration, cannot propagate as a 3D periodic structure and can occur only as a cluster in other, especially cubic, structures. It is not necessary that an entire structure exhibits a continuous pattern of close packing. In a large number of sulfosalts, and in some sulfides, layers, rods or even blocks of a closepacked or a distorted close-packed arrangement occur, joined to the adjacent such layers, rods or blocks, by interfaces on which certain cuts through the close-packed arrangement of anions face quite differently oriented cuts through (mostly) the same arrangement. For example, the pseudotetragonal (100) cuts through a P b S archetype (see below) often face (111) cuts through the same archetype. The keys to this arrangement are suitable cations, or lone electron pair cations, capable of spanning and populating this interface. Cation coordination. The preferred coordination of a cation in a chalcogenide structure depends on its size, charge and electron configuration. The cations with a "noble gas" (sp 3 ) configuration have coordinations according to their radius. The appropriate "crystal radii" for sulfides were derived by Shannon (1981) and appear to serve well in most instances. A necessary addition to his table is the tetrahedral radius of Cu 2+ , equal to ~0.51 A (Makovicky and Karup-M0ller 1994), as opposed to the 0.635 A given for Cu + in sulfides by Shannon (1981). Cations with d10 configurations prefer tetrahedral coordinations; the same is true for transition metals with maximum valencies. For spin-paired d8 configurations, such as in Pd 2+ and Pt 2+ , square-planar coordinations occur, whereas for such configurations of Ni 2+ , a squarepyramidal coordination is typical (Jellinek 1968). The same picture is obtained using the hybridization concept (e.g., Belov et al. 1982). Tetrahedral coordination is explained by the use of sp3 hybrid orbitals, octahedral by the use of cPsp3 orbitals, square planar is based on dsp2 orbitals, triangular is based on the sp2 hybridization (e.g., Cu + ), and the linear coordination of Cu + and Ag + results from an sp hybrid. These concepts are summarized in Table 1. Other crystal chemical concepts relevant to sulfides have been outlined by Prewitt and Rajamani (1974), Vaughan and Craig (1978), and Vaughan and Wright (1998) and are discussed elsewhere in this volume. Jahn-Teller distortions due to the differential occupancy of individual d orbitals are unusual among sulfides because of electron delocalization (Jellinek 1968) but they do explain the configurations found in Cr 2+ , Pd 2+ and Pt 2+ sulfides. The coordination properties of the cations need to find their counterpart in the anion packing. The majority of the cations in natural chalcogenides have coordination requirements that fit with the filling of tetrahedral, octahedral or other interstices in the anion arrays. Thus, ccp and hep offer coordination octahedra and regular tetrahedra, as well as a plethora of

Crystal Structures of Sulfides & Chalcogenides

9

Table 1. Coordination numbers and hybridization types for the cations commonly occurring in chalcogenides.

CN

Type of Hybridization

Category

2

sp; p2

Cu+, Cu2+, Ag+, Hg2+

3

sp 2

Cu+, Ag+

3

P3

As+, Sb3+, Bi3+, Pb2+ 3

4

sp

4(sq)

ilsjr 3

Cu+, Ag+, Au+; Zn2+, Cd2+, Hg2+; Ga3+, In3+, Tl3+; Ge4+, Sn4+; As5+, Sb5+; MnH2+,FeH2+ FeH3+, COh3+, NiH2+, NiH3+, Pd2+, Pt2+, Cu2+

5

dsp p3d2

NiL2+ Sb3+, Bi3+; Pb2+

6

d2sp3 sp3d2 p3; d2sp3

Fe L 2+ , Fe L 3+ , COL3+, NiL4+, PtL4+ Sn4+ Pb2+; Bi 3+ (Sb3+)

triangular coordinations at different structure sites. They preclude quadratic coordinations, whereas linear coordinations, such as S-Cu-S require a distortion of the anion array. Some coordinations, such as the trigonal prismatic coordination of the early Ad or 5d elements (Mo, W, Nb, Ta) change anion stacking schemes; the van der Waals intervals of layered structures tend to preserve them. The lone electron pair elements, As 3+ , Sb 3+ , Bi 3+ , Sn 2+ , Ge 2+ , and to a lesser extent Tl + and Pb2+, require an excessive, usually asymmetrically situated structural space for their non-bonding s2 pair. This volume is not comparable with that of the anion, which is the case in the oxides, with the relatively smaller O 2 - (Andersson et al. 1973). The degree of stereochemical activity of the lone pair varies with the species (decreasing with increasing Z) and the structure type. Structural classification Structural classifications generally employ a combination of the above criteria: the large scale structural configuration (3D/2D/1D character of principal building units), anion packing, bonding characteristics/type of coordination polyhedra of cations, and cation-cation and anion-anion interactions. These factors are used indirectly in the classification of Strunz and Nickel (2001) in which chalcogenides are divided into categories with M:S > 1:1, M:S = 1:1 (and derivatives), M:S = 3:4 and 2:3, andM:S < 1:2. Sulfosalts are classified separately, mainly according to their archetypes. Ross (1957) follows similar principles. Kostov and MincevaStefanova (1982) divide sulfide- and sulfosalt structures into axial, planar, pseudoisometric and isometric types, using the axial ratios of their lattices as an expression for the anisotropy of strongest bonds in the structure. The classification of Povarennykh (1972) is similar, although more "classical" in the choice of categories. Takeuchi (1970) and Parthe (1990) divide chalcogenides into polyanionic, polycationic and normal-valence compounds based on Pearson's valence rule. Belov et al. (1982) discern normal-, cluster-, molecular-, and polyanionic chalcogenides, as well as distinct cation coordinations in the compound. Vaughan and Craig (1978), Robert and Makovicky (1984) and Vaughan and Wright (1998) define chalcogenide groups based on well-known structure types, each of them unifying a number of the above defined structural criteria, in which they include a number of iso-, homeo-, and poly-types as well as interstitial and omission derivatives, eventually even homologues and plesiotypes. An updated overview of the most important groups is given in Table 2.

Makovicky

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