Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, Brittle, Metallic, Brittle, Metallic, Brittle, Metallic
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Na,Fe,Ca)Si 2O 6Ulrich Henn and Claudio C.