Afghanistan, Pakistan, Burma, Brazil, Madagascar, USA, Canada, Russia, Madagascar, Brazil, Canada, Mexico, Madagascar, Brazil, Canada, Mexico
Not Available, Southern and central Africa
Gemstones of the world (2001), UnevenWalter Schumann, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)