UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca 2 MgAl 2 BSi 4 O 15 OH Gemdat.org, Management Team (2012)