Conchoidal, Splintery, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
AlPO4 · 2(H2O)
(Na,Ca) 8Al 6Si 6O 24(SO 4,S,Cl) 2Ulrich Henn and Claudio C.