Tanzanite
Tanzanite is the transparent blue variety of zoisite, a hydrous calcium aluminium silicate mineral. It was discovered in 1967 in Tanzania, East Africa, which remains the only known mining location. Colours range mainly from a sapphire blue to a violet blue and it is commonly heat treated to enhance colour. A rare and extremely popular stone. Birthstone for December. Hardness: 6.5 (Mohs).