Ch. 12: Other Precious Stones

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	OTHER PRECIOUS STONES Several weighing over 100 carats, are exhibited from time to time at the courts of Europe. Topaz, zircon, emerald, garnet, quartz, amethyst, onyx, agate, opal, and pearls found in the shells of oysters are made up of the composition of silica, carbonates and organic matter. The topaz affords a striking illustration of the vicissitudes of fashion. A century ago this brilliant yellow gem, which is identical with the ruby and sapphire in everything but color, was nearly as valuable as they. Now it has no value worth mentioning as a jewel, and is chiefly used for optical purposes and by clock-makers. The bluish-violet mineral hyacinth has been known for many years as an inferior gem-stone. The name hyacinth is not altogether a good one, although it has been applied by jewelers to all of the zircon gems. Zirconium does not occur free in nature. As a mineral, zircon is found chiefly in India and Ceylon. Zircon is essentially an Oriental gem. It is found in the sand as grains. Zircon is much oftener met with in the bazaars of Ceylon than in the jewelry shops of Fifth Avenue and the Rue de la Paix. The sixth of the seven Moslem heavens is said to be composed of yellow jacinth, which is one of the names for the gem zircon. In hardness zircon is 7.5, rather harder than quartz but not as hard as topaz. It is therefore not altogether suitable as a ring stone, but with a range of color that is highly attractive and an index of refraction that enables them, when cut, to rival the diamond in brilliancy. With all the strik- 113

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