The name after Tanzania was introduced by the New York jewelers Tiffany&Co. The only deposit are found near Arusha (Tanzania), it occurs in veins or filling of fissures of gneisses. It appears a storng pleochorisim to purple, brown or yellow.
Moh's hardness: 6.5-7
Chemical composition: Ca2Al3 [ O[OH][SiO4]Si2O7] Calcium aluminium silicate