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
CaZnSiO 4 · H 2OAnthony et al , Handbook of mineralogy (2001)