The name Tanzanite comes from Tanzania the only know source of gem quaility. Tanzanite is normally heated to 752-932 degrees f to remove any green or yellow tints this also darkens the blue colour. Green and pink Tanzanite are extremly rare but do appear every now and then. The only depsoit is in Tanzania near to Arusha. Other known transparent varitys do exist. It has a mohls hardness of 6.5-7 and a refractive index of 1.691-1.700