ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Al 2Be 3Si 6O 18Martin H.
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references