Tanzanite << TAN zuh nyt >> is a semiprecious gemstone. It is a variety of a mineral called zoisite. Tanzanite crystals are trichroic (three-colored). As the gemstone is turned, its color changes from deep blue to purple to yellowish-green. When heat is applied to the crystals, they become uniformly blue. The blue color is most popular, so the majority of tanzanite is heat-treated.
Tanzanite is cut into gemstones with numerous facets (flat, polished surfaces), which emphasize its light-reflecting quality. The gemstones are used in such jewelry as rings, earrings, and pendants.
Tanzanite was discovered in 1967 in Tanzania, for which it was named. Tanzania is the only known source of tanzanite. Because the supply is limited, the gemstones are expensive.
