Dichroite, 266 Dichroscope, 55 Diffusion column, 65 Diopside, 272 Dioptase, 280 Dispersion, Colour, 20, 24, 97 Disthene, 273 Dop, 102 Double refraction, 28, 40 Doublet, 125 Dresden diamond, 171 Drop-stone, 94 Duke of Devonshire’s emerald, 191 Edwardes ruby, 175 Electrical characters, 82 Emerald, 89, 184 Brazilian, 220, 221 Evening, 225 Oriental, 111, 172 Scientific, 122 Uralian, 216 Emeraldine, 247 Emery, 175 English Dresden diamond, 166 Enstatite, 271 Epidote, 275 Essence d’Orient, 126 Essonite (Hessonite), 211 Euclase, 269 Eugénie diamond, 164 Evening emerald, 225 Excelsior diamond, 167 Extinction, 45 Faceting machine, 105 False topaz, 239 Felspar, 254 Fire, 20, 96 Fire-marble, 289 Fire-opal, 251 Flats, 150 Flêches d’amour, 240 Flint, 247 Floors, 147 Fluor, 285 Frémy, E., 115 Garnet, 207 Green, 271 Gaudin, M. A. A., 115 Gauges, Diamond, 86 Girdle, 92 Glass, 7, 124 Gnaga Boh ruby, 180 Goniometer, 30 Grain, Pearl, 86 Graphite, 129 Greaser, 149 Great Mogul diamond, 161 Great Southern Cross group of pearls, 294 Great Table diamond, 162 Great White diamond, 167 Green garnet, 271 Greenstone, 261 Grossular, 211 Habit, 12 Hardness, 78 Haüynite, 286 Heavy liquids, 64 Hematite, 282 Hessonite, 211 Hexagonal system, 10 Hiddenite, 266 Hope cat’s-eye, 237 chrysolite, 237 diamond, 170 pearl, 294 sapphire, 121 Hornstone, 247 Hungarian cat’s-eye, 244 Hyacinth, 211, 228 Hydrophane, 250 Hydrostatic weighing, 72 Hypersthene, 271 Iceland-spar, 40, 44 Idocrase, 274 Imitation stones, 124 Imperial diamond, 167 Index of refraction, 16 India stones, 137, 181, 194, 215, 243, 244, 248, 290 Indicators, 65 Indicolite, 221 Interference of light, 39, 48 Iolite, 266 Iris, 240 Isle of Wight diamonds, 243 Isomorphous replacement, 13, 19 Jacinth, 211, 228 Jade, 260 Jadeite, 262 Jargoon, 228 Jasper, 247 Jehan Ghir Shah diamond, 163 Jigger, 149 Jubilee diamond, 167 Kauri-gum, 299 Khiraj-i-Alam ruby, 206 Kimberlite, 152 King topaz, 181, 201 Klein’s solution, 67 Koh-i-nor diamond, 137, 158 Kunz, Dr. G. F., 186, 224, 262, 265 Kunzite, 265 Kyanite, 79, 273 Labradorite, 255 La Pellegrina pearl, 294 Lapis lazuli, 286 Lazurite, 286 Lozenge facet, 93