UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)