ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
SiO 2Walter Schumann , Gemstones of the world (2001)
CaBePO 4(F,OH)Ulrich Henn and Claudio C.