Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Ca 5(PO 4) 3FAnthony et al , Handbook of mineralogy (2001)
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references