ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Uneven, Gems, Sixth Edition (2006), Uneven, Conchoidal
Al 2Be 3Si 6O 18Martin H.
NaAlSi 3O 8Michael OâDonoghue , Gems, Sixth Edition (2006)