Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, Gemstones (2009), Splintery
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca 2NaHSi 3O 9Ulrich Henn and Claudio C.