ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Al 2Be 3Si 6O 18Martin H.
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references