Uneven, Uneven, Gems, Sixth Edition (2006), Uneven, Conchoidal
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
NaAlSi 3O 8Michael OâDonoghue , Gems, Sixth Edition (2006)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.