Brittle, Metallic, Brittle, Metallic
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Conchoidal
Be 4Si 2O 7(OH) 2Anthony et al , Handbook of mineralogy (2001)
PbCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references