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
Na 2ZrSi 3O 9 · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006)