China, Russia
Afghanistan, Brazil, Southern and central Africa, Madagascar, Russia, USA, Zimbabwe
Uneven, Conchoidal, Brittle, Metallic, ConchoidalArthur Thomas, Gemstones (2009)
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)