Splintery, UnevenArthur Thomas, Difficult, Fibrous
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
NaAlSi 2O 6Ulrich Henn and Claudio C.
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references