Conchoidal, ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
SiO 2Ulrich Henn and Claudio C.
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references