ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.