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