Lumachelle, 289 Lustre, 37 Maacles, Macles, 12, 150 Madagascar stones, 195, 224, 243, 265, 266 Malachite, 287 Malacolite, 272 Manufactured stones, 113 Marble, 289 Mattan diamond, 155, 170 Matura diamonds, 232 Mazarin, Cardinal, 92 Meerschaum, 288 Mêlée, 136 Methylene iodide, 26, 66 Metric carat, 85, 87 Milky-quartz, 240 Minimum deviation, 30 Mocha-stone, 247 Moe’s gauge, 87 Mohs’s scale of hardness, 78 Moissan, Henri, 153 Moldavite, 283 Monoclinic system, 11 Moon of the Mountains diamond, 162 Moonstone, 39, 255 Morganite, 186, 195 Moroxite, 279 Moss-agate, 247 Mother-of-emerald, 240 Mother-o’-pearl, 292 Nacre, 292 Napoleon diamond, 164 Nassak diamond, 163 Negative double refraction, 45 Nephrite, 261 Nicol’s prism, 44 Nizam diamond, 162 Obsidian, 283 Occidental topaz, 111, 239 Odontolite, 259 Off-coloured diamonds, 130 Olivine (demantoid), 216 (peridot), 225 Onyx, 247 Opal, 39, 249 Fire, 251 -matrix, 251 Opalescence, 39 Optical anomalies, 47 Optic axes, 49 Oriental almandine, 112, 172 amethyst, 111, 172 emerald, 111, 172 topaz, 111, 172 Orient of pearls, 292 Orloff diamond, 160 Orthoclase, 254 Orthorhombic system, 11 Pacha of Egypt diamond, 165 Paste, 47, 124 Paul I diamond, 171 Pavilion, 93 Pavilion facet, 93 Pear-drop pearls, 292 Pear-eye pearls, 292 Pearl, 291 grain, 86 imitations, 126 Pendeloque, 94 Peridot, 225 Brazilian, 221 Ceylonese, 221 Peruzzi, Vincenzio, 92 Phenakite, 269 Pigott diamond, 164 Pipes, 152 Pistacite, 275 Pitt diamond, 100, 159 Plasma, 247, 264 Pleochroism, 57 Pleonaste, 204 Pliny, 6, 88, 138, 184, 191, 241, 249 Polar Star diamond, 163 Polarization, 42 Porter-Rhodes diamond, 166 Positive double refraction, 45 Prase, 240, 247 Prehnite, 278 Pycnometer, 75 Pyrites, 282 Pyrope, 212 Quartz, 50, 238 Quoin facet, 93 Rainbow-quartz, 240 Reconstructed stones, 116 Reef, 144 Reflection of light, 14 Refraction of light, 15 Refractive index, 16 Refractometer, 22, 50 Regent diamond, 100, 159 Retgers’s salt, 69 Rhodes, Cecil J., 145 Rhodesia stones, 155, 183, 213, 236 Rhodolite, 62, 214 Rhodonite, 287 Rock-crystal, 97, 239 Rock-drill, 134 Röntgen rays, 83 Rose form of cutting, 91 Rose-quartz, 240 Rospoli sapphire, 182