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

PRECIOUS STONES DISTINGUISHED BY THEIR _PROPERTIES_. One precious stone
is best distinguished from another just as substances of other types are
distinguished, that is to say, by their _properties_. For example, salt
and sugar are both _white_, both are _soluble in water_, and both are
_odorless_. So far the italicized properties would not serve to
distinguish the two substances. But sugar is _sweet_ while salt is
_salty_ in taste. Here we have a distinguishing property. Now, just as
salt and sugar have properties, so have all _precious stones_, and
while, as was the case with salt and sugar, many precious stones have
properties in common, yet each has also some properties which are
distinctive, and which can be relied upon as differentiating the
particular stone from