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