ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Conchoidal, Splintery, Fibrous, UnevenArthur Thomas, Gemstones (2009)
SiO 2Ulrich Henn and Claudio C.
CaSO 4 -2(H 2O)Arthur Thomas , Gemstones (2009)