Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references
Ca 9(Mg,Fe2+ )(PO 4) 6(PO 3OH)Anthony et al , Handbook of mineralogy (2001)