Gems, Sixth Edition (2006), Gems, Sixth Edition (2006), Uneven
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Na(90-70%)Ca(10-30%)(Al,Si)AlSi 2O 8Michael OâDonoghue , Gems, Sixth Edition (2006)
ZrO 2Arthur Thomas , Gemstones (2009)