Chemical Composition: Calcium aluminium silicate with hydroxyl (OH)
Refractive Index: 1.69 – 1.70
Specific Gravity: 3.15 – 3.38
Crystal System: Orthorhombic
Moh's Hardness: 6 ½

Tanzanite is the transparent blue variety of zoisite and was discovered as a new gem in 1967. Colour ranges between blue to violet. Alternatively zoisites of transparent nature are heat treated to produce the blue violet colour.

Locality for Tanzanite is Tanzania.