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