VIII.--HARDNESS 47 IX.--HARDNESS (_Continued_) 55 X.--DISPERSION 60 XI.--COLOR 66 XII.--COLOR (_Continued_) 75 XIII.--COLOR (_Continued_) 87 XIV.--COLOR (_Concluded_) 93 XV.--HOW TO TELL SCIENTIFIC STONES FROM NATURAL GEMS 99 XVI.--HOW TO TEST AN "UNKNOWN" GEM 109 XVII.--SUITABILITY OF STONES FOR VARIOUS TYPES OF JEWELS, AS DETERMINED BY HARDNESS, BRITTLENESS, AND CLEAVABILITY 119 XVIII.--MINERAL SPECIES TO WHICH THE VARIOUS GEMS BELONG AND THE CHEMICAL COMPOSITION THEREOF 133 XIX.--THE NAMING OF PRECIOUS STONES 149 XX.--THE NAMING OF PRECIOUS STONES (_Concluded_) 164 XXI.--WHERE PRECIOUS STONES ARE FOUND 179 XXII.--HOW ROUGH PRECIOUS STONES ARE CUT 201 XXIII.--HOW ROUGH PRECIOUS STONES ARE CUT AND WHAT CONSTITUTES GOOD "MAKE" (_Concluded_) 213 XXIV.--FORMS GIVEN TO PRECIOUS STONES 227 XXV.--IMITATIONS OF PRECIOUS STONES 237 XXVI.--ALTERATION OF THE COLOR OF PRECIOUS STONES 250 XXVII.--PEARLS 258 XXVIII.--CULTURED PEARLS AND IMITATIONS OF PEARLS 277 XXIX.--THE USE OF BALANCES AND THE UNIT OF WEIGHT IN USE FOR PRECIOUS STONES 283 XXX.--TARIFF LAWS ON PRECIOUS AND IMITATION STONES 294 BIBLIOGRAPHY 301 INDEX 313 A Text-Book of Precious Stones LESSON I HOW STONES ARE DISTINGUISHED FROM ONE ANOTHER