Uneven, Brittle, Metallic, Brittle, Metallic
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
NaNa2(Fe++4Fe+++)Si8O22(OH)2
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references