Handbook of mineralogy (2001), Difficult, Fibrous
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ca 6Si 6O 17(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
Pb 5(AsO 4) 3ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references