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 5(PO 4) 3FAnthony et al , Handbook of mineralogy (2001)