ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references