Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Na 2(Ti,Fe)Si 4(O,F) 11Ulrich Henn and Claudio C.
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)