"Mixed cut" stones, 236 Mohs's scale of hardness, 48-51 Moonstone, 44, 45, 131, 146, 176, 198 Morganite, 165 "Nacre," 280 Naming precious stones, 149-163, 164-178 Nephrite, 129, 197 Occurrence of precious stones, 179-200 "Olivine" (_see_ Demantoid Garnet) Olivine, 83, 176 Onyx, 172 Opal, 44, 131, 139, 173 Ordinary ray, 16 "Orient" of pearls, 261 "Oriental" stones, 84, 156 "Paste" gems, 142, 237-241 Pearls, 258-276 "Peeling" pearls, 265 Peridot, 8, 130, 176, 198 Pink stones, 93 "Pinked" topaz, 250 Plasma, 172 Polishing of diamonds, 210 Polishing of precious stones, 218 Prase, 138, 172 Properties, definition of, 1 Purple stones, 94 Quartz, aventurine, 171 Quartz, citrine, 161, 171, 195, 196 Quartz gems, 45, 127, 171, 195, 197 Reflection, total, 204 Refraction, 4 Refraction, double, 8-13 Refraction, double, test for, 10, 112 Refractometer, 5 Rhodolite garnet, 168 "Roman" pearls, 279 Rose cut stones, 231 Rose quartz, 171, 197 Rubellite, 93 Ruby, 12, 67, 69, 153, 154, 186 Ruby, scientific, 99-108 Sapphires, 63, 87, 88, 155, 187 Sard, 172 Sardonyx, 172 Scientific stones, 99-108 Scientific stones, defects in, 104 Scientific stones, tests for, 99-108 Siam rubies, 154 Silicates, 141 "Silk" in rubies, 117 Slitting of precious stones, 213 South African diamonds, 184 Specific gravity, 23-37, 114 Sphene, 9, 62, 64 Spinels, 71, 90, 123, 140, 158, 188 Spodumene, 95, 170, 195 Star stones, 44, 46, 157 "Step cut" stones, 235 Structure of pearls, 258 Table, of hardness, 54 Table of refraction, 12-13 Table of specific gravity, 29 Tariff laws, 294-299 Test for double refraction, 10 Testing hardness, 51-54, 58 Testing imitations of pearls, 281 Testing unknown gems, 109-118 Tiger's-eye, 45, 138, 171 Topaz, 67, 73, 91, 124, 145, 159, 189 Toughness in stones, 119 Tourmaline, 72, 77, 79-81, 96, 146, 167, 194 "Triplets," 79, 246 Turquoise, 130, 148, 198 Unit of weight, 289 Variscite, 148 Vitreous luster, 41 Wearing qualities of gems, 119 Zircon, 9, 62, 72, 92, 97, 125, 147, 166, 191 Diamonds A Study of the Factors that Govern their Value By Frank B. Wade "I shall speak a little more of the diamonds, that they who know them not may not be deceived by chapmen who go through the country selling them, for whoever will buy the diamond, it is needful that he know them, ..."--Chap. XIV., _The Voyages and Travels of Sir John Maundeville_. _Table of Contents_ I.--Colour. II.--Flaws. III.--"Make." IV.--Repairing and Recutting. V.--Mounting. VI.--Buying the Engagement Ring.