Color : Sapphire blue, amethyst, violet 
Color of streak: White
Mohs� hardness : 6.5-7
Specific gravity : 3.35   
Cleavage : Perfect 
Fracture: Uneven, brittle 
Crystal system : Orthorhombic
Chemical composition : Calcium aluminium silicate
Refractive index : 1.691-1.700
Double refraction : +0.009 
Flourescence : None

The name tanzanite (after the East African state of Tanzania) was introduced be the New York jewelers Tiffany & Co. It is accepted by the trade, although scientists do not encourage a multitude of names for gemstones and refer to it as blue zoisite. In good quality the color is ultramarine to sapphire blue; in artificial light, more amethyst violet. When heated to 752-932 F / 400-500 C, the yellow and brown tints vanish, and the blue deepens. Tanzanite cat�s eyes are also found. Some deposits in Tanzania near Arusha occur in veins or filling of fissures of gneisses.