Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, Conchoidal, Gemstones of the world (2001)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references