ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
ZrO 2Arthur Thomas , Gemstones (2009)
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)