Topaz << TOH paz >> is a white or light-colored mineral sometimes cut into gems. It is a compound of aluminum, fluorine, silicon, oxygen, and hydrogen. Its chemical formula is Al2(SiO4)(OH,F)2. Trace impurities give topaz crystals a wide variety of colors. Topaz is hard. It defines an 8 on the Mohs hardness scale, a ranking of mineral hardness commonly used by geologists. Small amounts of topaz occur in some igneous rocks, rocks that form when molten rock cools and solidifies, and metamorphic rocks, rocks that have been changed by heat and pressure.
Jewelers cut transparent topaz crystals into gems. The most desirable topaz gems range in color from completely colorless to gold, orange, blue, and pink. Exposing some topaz crystals to heat or radiation can dramatically enhance or even change their color. Jewelers sell blue topaz as a substitute for the gem aquamarine. Citrine, a yellow or brownish variety of quartz, is sometimes sold as a substitute for topaz.
Topaz is found in many parts of the world. Brazil produces most of the world’s gem-quality topaz. Many museum collections have large, beautiful topaz crystals that weigh hundreds of pounds or kilograms. Topaz is the birthstone for November.
