Page 9 - A Practical Introduction to Optical Mineralogy

CONTENTS CONTENTS
Scapolite 117; Serpentine 119; Silica group 120; 5 Reflected-light theory
Sphene 124; Staurolite 125; Talc 126; Topaz 127; 5.1 Introduction page 202
Tourmaline group 128; Vesuvianite 129; 5.1.1 Reflectance 203
Zeolite group 129; Zircon 131 5.1.2 Indicating surfaces of reflectance 206
5.1.3 Observing the effects of crystallographic
orientation on reflectance 206
3 The non-silicates 5.1.4 Identification of minerals using reflectance
measurements 209
3.1 Introduction page 132 209
3.2 Carbonates 132 5.2 Colour of minerals in PPL 210
3.3 Sulphides 138 5.2.1 CIE (1931) colour diagram 211
3.4 Oxides 154 5.2.2 Exercise on quantitative colour values 212
3.5 Halides 167 5.3 Isotropic and anisotropic sections 212
3.6 Hydroxides 169 5.3.1 Isotropic sections 213
3.7 Sulphates 171 5.3.2 Anisotropic sections 213
3.8 Phosphate 175 5.3.3 Polarisation colours 215
5.3.4 Exercise on rotation after reflection
3.9 Tungstate 175
5.3.5 Detailed observation of anisotropy 216
3.10 Arsenide 176
3.11 Native elements 177
Appendix A.1 Refractive indices of biaxial minerals 218
Appendix A.2 Refractive indices of uniaxial positive minerals 219
4 Transmitted-light crystallography Appendix A.3 Refractive indices of uniaxial negative minerals 220
Appendix A.4 Refractive indices of isotropic minerals 221
4.1 Polarised light: an introduction 180
Appendix B 2V and sign of biaxial minerals 222
4.2 Refractive index 181 Appendix C Properties of ore minerals 225
4.3 Isotropy 181 Appendix D Mineral identification chart 237
4.4 The biaxial indicatrix triaxial ellipsoid 183 Appendix E Gangue minerals 239
4.5 The uniaxial indicatrix 184
4.6 Interference colours and Newton's Scale 186 Bibliography 241
4.7 Fast and slow components, and order
Index 243
determination 190
4.7.1 Fast and slow components 190
4.7.2 Quartz wedge and first order red accessory
plate 191
4.7.3 Determination of order of colour 191
4.7.4 Abnormal or anomalous interference
colours 192
4.8 Interference figures 192
4.8.1 Biaxial minerals 192 List of tables
4.8.2 Sign determination for biaxial minerals 196
4.8.3 Flash figures 196
4.8.4 Uniaxial minerals 197 1.1 Optical data for air and oil immersion page 22
4.8.5 Isotropic minerals 197 1.2 Relation between VHN and Moh's hardness 27
4.9 Pleochroic scheme 197 3.1 Optical properties of the common carbonates 134
4.9.1 Uniaxial minerals 197 3.2 Spinels 158
4.9.2 Biaxial minerals 200 4.1 Extinction angle sections not coincident with
4.10 Extinction angle 200 maximum birefringence sections 201

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