UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Handbook of mineralogy (2001), Difficult, Fibrous
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
Ca 6Si 6O 17(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)