Topaz

Topaz, variety of mineral aluminum fluosilicate, crystallized in the orthorhombic system (see Crystal), and valued as a gem. It has a vitreous luster and may be colorless, yellow, green, blue, or red. It has a hardness of 8 and a specific gravity of 3.4 to 3.6. Topaz occurs in gneiss or granite associated with beryl, mica, and tourmaline and occasionally with apatite, cassiterite, and fluorite; it also occurs in certain talcose rocks, mica slate, rhyolite, and in alluvial deposits and drift. The crystallized varieties, owing to their hardness, are valued as gems, and the best of these come from Sri Lanka and parts of India, the Ural Mountains in Russia, and Minas Gerais State, Brazil; and in the U.S. from Maine, Colorado, and Utah. The most popular color for topaz gemstones is a rich orange-yellow, resembling the color of sherry wine. Rose topaz is a delicate rose pink. It is the birthstone for November. The true Oriental topaz is the yellow sapphire, and the Saxon, Scottish, Spanish, smoky, and false topaz are yellow varieties of quartz. See Gemstones.