Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)