Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Brittle, Metallic, Brittle, Metallic
CaB 2(SiO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 2ZrSi 3O 9 · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)