UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
ConchoidalAnthony et al, Handbook of mineralogy (2001), ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaBe 2(PO 4) 2Michael OâDonoghue , Gems, Sixth Edition (2006)