Australia, Canada, Guatemala, Italy, Kenya, Mexico, Turkey, Mexico, Guatemala, Mexico, Guatemala
Afghanistan, Brazil, Southern and central Africa, Madagascar, Russia, USA, Zimbabwe
Conchoidal, ConchoidalWalter Schumann, Conchoidal
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)