Uneven, Uneven, Gems, Sixth Edition (2006)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
CaAl 2Si 2O 8Michael OâDonoghue , Gems, Sixth Edition (2006)
CaCO 3Ulrich Henn and Claudio C.