Topaz
This precious stone is found in Saxony, Bohemia, Siberia, and Brazil, mixed with other minerals in granite rocks. its colors are yellow, bluish, greenish, lilac, and white. Electric by heat, but not by rubbing. It is composed of alumina 47.5, silex 44.5, fluoric acid 7, oxide of iron 0.5. This is for the yellow variety; their compositions vary. It occurs crystallized and in water-worn pebbles, being harder than quartz, but hardly as hard as the ruby. The yellow variety, when without flaws, is employed for jewelry. See SAPPHIRE; PRECIOUS STONES.