Introduction to Practical Ore Microscopy

Preface and Acknowledgements ix
CHAPTER 1 INTRODUCTION 1
CHAPTER 2 THE ORE MICROSCOPE 2
2.1 General comments 2
2.2 The rotatable stage 3
2.3 The objective lens(es) 4
2.4 The ocular (eyepiece) lens(es) 6
2.4.1 Care and cleaning of lenses 6
2.5 The polariser and analyser 6
2.6 The reflector 7
2.7 The light source (illumination, illuminator) 7
2.8 Sample holder 8
2.9 Mechanical stage 8
2.10 Eyepiece and stage micrometers 9
2.11 Photometer 9
2.12 Monochromators and filters 9
CHAPTER 3 SAMPLE PREPARATION 10
3.1 General comments 10
3.2 Preparation 10
3.3 Grinding and polishing 11
3.3.1 Vibropolishing 13
3.3.2 Electrolyte polishing 13
3.4 Polished thin sections 13
3.5 Etching 14
3.6 Grain mounts 14
3.7 Sample storage 14
CHAPTER 4 MINERAL IDENTIFICATION 16
4.1 Simple optical techniques 16
4.1.1 Introduction 16
4.1.2 Colour 17
4.1.3 Bireflectance and reflection pleochroism 18
4.1.4 Crossed polars anisotropy 19
4.1.5 Internal reflections 22
4.2 Reflectance 23
4.2.1 General comments 23
4.2.2 Qualitative methods 23
4.2.3 Quantitative methods 24
4.3 Simple physical techniques 30
4.3.1 Introduction 30
4.3.2 Crystal morphology (forms and habits) 31
4.3.3 Zoning 32
4.3.4 Cleavage and parting 32
4.3.5 Twinning 33
4.3.6 Inclusions and intergrowths 34
4.3.7 Tenacity 34
4.3.8 Streak 34
4.4 Hardness 34
4.4.1 Polishing hardness 35
4.4.2 Scratch hardness 35
4.4.3 Microindentation hardness 35
CHAPTER 5 TEXTURES OF THE ORE MINERALS 38
5.1 Introduction 38
5.2 Descriptive textures 38
5.2.1 Single grains 38
5.2.2 Aggregates 49
5.3 Genetic textures due to primary deposition 52
5.3.1 Growth fabric textures 52
5.3.2 Colloidal textures 57
5.3.3 Sedimentary textures 59
5.4 Genetic textures resulting from transformation 60
5.4.1 Paramorphic replacement texture 60
5.4.2 Exsolution - simple and complex 61
5.4.3 Replacement textures 66
5.4.4 Relic(t) textures 73
5.4.5 Decomposition textures 73
5.4.6 Oxidation (weathering) textures 73
5.4.7 Cementation textures 75
5.5 Deformation textures 75
5.5.1 Curvature of linear features 75
5.5.2 Schlieren 76
5.5.3 Brecciation or cataclasis 76
5.6 Annealing textures 76
5.6.1 Recrystallisation textures 76
5.6.2 Re-equilibration textures 77
5.7 Metamorphic textures 77
5.7.1 Dynamic metamorphic effects 77
5.7.2 Thermal metamorphic effects 78
5.7.3 Skarns 79
5.8 Miscellaneous or special textures 80
5.8.1 Framboids or framboidal texture 80
CHAPTER 6 PARAGENESIS 81
6.1 Introduction 81
6.2 Aids in erecting a paragenetic sequence 83
6.2.1 Crystal shape 83
6.2.2 Relict (pseudomorphic) complexities 83
6.2.3 Mutual grain boundary problems 84
6.2.4 Colloform banding 84
6.2.5 Growth zoning 84
6.2.6 Cross-cutting relationships 84
6.2.7 Twinning 84
6.2.8 Exsolution 85
6.2.9 Replacement 85
6.2.10 Fluorescence 85
6.2.11 Additional reading 86
CHAPTER 7 STRUCTURAL ETCHING 87
7.1 General comments 87
7.2 The method 87
7.3 The reagents 88
CHAPTER 8 MINERAL TABLES 89
8.1 Introduction and explanation of the tables 89
Argentite 91
Arsenopyrite 93
Bismuthinite 94
Bomite 96
Boulangerite 97
Cassiterite 99
Chalcocite 100
Chalcopyrite 102
Chromite 103
Cinnabar 104
Cobaltite 105
Copper 106
Covellite 107
Cubanite 108
Cuprite 110
Enargite 111
Galena 112
Goethite 114
Gold 115
Graphite 116
Hematite 117
Ilmenite 119
Lollingite 120
Magnetite 121
Manganite 122
Marcasite 123
Millerite 125
Molybdenite 126
Niccolite 127
Pentlandite 128
Platinum 129
Proustite 130
Psilomelane 131
Pyrargyrite 132
Pyrite 133
Pyrolusite 134
Pyrrhotite 135
Rutile 136
Scheelite 138
Silver 139
Sphalerite 140
Stannite 141
Stibnite 142
Sylvanite 144
Tennantite 145
Tetrahedrite 146
Uraninite 147
Wolframite 148
APPENDIX 1 COMMON MINERAL ASSEMBLAGES OR ASSOCIATIONS 149
APPENDIX 2 DIAGRAM OF OPTICAL DETERMINATIONS OF THE ORE MINERALS ON THE BASIS OF REFLECTANCE VALUES (FOR 589 nm) AND MICROHARDNESS (VHN) 167 
APPENDIX 3 REFLECTED LIGHT OPTICS 168
APPENDIX 4 LIST OF ABBREVIATIONS 171
References 173
Index 177