Beginner's Guide to Gemmology (eBook)

Front Cover 1
Beginner's 
4 
Copyright Page 5
Table of Contents 7
Preface 6
Chapter 1. Gemmology,the Science of Gem Materials 8
The essential qualities of a gem material 10
Gem minerals 12
Rock and gemstone formation 13
The composition and characteristics of gemstones 17
Groups, species and varieties 19
Use of the hand lens and microscope 21
Chapter 2. Colour, Lustre and Sheen 27
Selective absorption 28
Aliochromatic and idiochromatic gemstones 30
The transition elements 30
The optics of lustre and sheen 35
Transparency 39
Artificial coloration 40
Chapter 3. Crystallography, the Science of Crystal Structures 43
Elements of symmetry 44
The seven crystal systems 46
Identification of rough gem samples by shape 53
Crypto-crystalline gems 56
The metamict state 60
Suppliers of mineral specimens 60
Chapter 4. Hardness, Fracture, Cleavage and Parting 61
Mohs scale 61
Directional hardness 63
Characteristic fractures 66
Cleavage planes 67
False cleavage or parting 69
Chapter 5. Specific Gravity 70
Displacement method of SG determination 71
Hydrostatic weighing 72
Heavy liquids 77
Safety precautions 83
Testing for amber 84
Suppliers of SG test equipment 84
Chapter 6. Refractive Index and Double Refraction 85
Approximation of RI by immersion 87
Approximation of RI using Becke line method 88
Direct method of RI measurement 89
Measurement of RI using a refractometer 90
Double refraction and its measurement 96
Optical character and optic sign 98
Using the critical angle refractometer 99
Distant vision method 100
Special refractometer versions 101
The table spectrometer 103
The polariscope 105
The konoscope 108
Instrument developments 108
Chapter 7. The Optics of Polished Gemstones 109
Dispersion 112
Reflectivity 114
Critical angle 119
Gemstone cuts 124
Gemstone polishing 129
Chapter 8. Absorption and Emission Spectra 133
The prism spectroscope 134
The diffraction grating spectroscope 137
Use of spectra for gemstone identification 138
Fine line spectra and the rare earths 144
Using the spectroscope 144
Chapter 9. Luminescent and Electrical Properties of Gems 147
Crossed filters 149
Long-wave ultraviolet lamps 150
Short-wave ultraviolet lamps 151
X-ray equipment 152
Identifying gemstones by luminescence 153
Electrical properties 158
Chapter 10. Organic Gem Materials and their Simulants 160
Pearls 160
Cultured pearls 161
Non-nucleated pearls 162
Distinguishing natural from cultured pearls 163
Imitation pearls 167
Mother-of-pearl and cameos 168
Amber 169
Ivory 171
Odontolite 172
Tortoiseshell 173
Jet 173
Chapter 11. Synthetic Gemstones 176
The Vemeuil flame fusion process 177
Coral 175
The Czochralski process 181
The Bridgeman-Stockbarger process 181
The 'skull' crucible process 182
The hydrothermal process 182
The flux melt process 185
Synthetic diamond production 186
Distinguishing synthetic from natural gemstones 188
Emerald 189
Ruby 192
Sapphire 193
Alexandrite 196
Opal 196
Spinel 198
Turquoise 199
Lapis lazuli 199
Quartz 200
Chapter 12. Gemstone Simulants 201
Alexandrite simulants 201
Aquamarine simulants 202
Diamond simulants 202
Emerald simulants 207
Jade simulants 208
Lapis lazuli simulants 209
Ruby shnulants 210
Sapphire simulants 211
Turquoise simulants 212
Paste simulants 213
Composite stones 213
Appendix A 217
Appendix B 224
Units of measurement 231
Miller indices 232
Appendix C Bibliography 235
Appendix D Examination Notes 236
Theory papers 236
Practical paper 237
Index 238