Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Ca 2 MgAl 2 BSi 4 O 15 OH Gemdat.org, Management Team (2012)
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)