Uneven, Uneven, Gems, Sixth Edition (2006), Uneven, Conchoidal
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
NaAlSi 3O 8Michael OâDonoghue , Gems, Sixth Edition (2006)
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.