Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, Brittle, Uneven, Brittle, Uneven
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(K,Na)Ca4Si8O20(F,OH)•8(H2O)