Sugilite

This sample of sugilite is displayed in the Smithsonian Museum of Natural History. Sugilite is a silicate mineral which contains lithium. It has the composition KNa₂Li₃(Fe,Mn,Al)₂Si₁₂O₃₀. This sample is about 10 cm long and the gem is 23.5 carats. It is from Kalahari Desert, Cape Province, South Africa.