Uneven, Conchoidal, Brittle, Metallic, ConchoidalArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Ca 3Cr 2(SiO 4) 3Ulrich Henn and Claudio C.
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)