Handbook of mineralogy (2001), Difficult, Fibrous
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Ca 6Si 6O 17(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)