ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Conchoidal, UnevenArthur Thomas, Brittle
Al 2Be 3Si 6O 18Martin H.
Fe2+ CO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references