Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Metallic
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Mg 2Si 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 2Be 3Si 6O 18Martin H.