Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, Uneven, Gems, Sixth Edition (2006), Uneven, Conchoidal
(Mg,Fe) 5(SiO 4) 2(F,OH) 2Ulrich Henn and Claudio C.
NaAlSi 3O 8Michael OâDonoghue , Gems, Sixth Edition (2006)