UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.