UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.