Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
UnevenAnthony et al, Handbook of mineralogy (2001), UnevenAnthony et al, Handbook of mineralogy (2001), Uneven
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references
Fe3+ PO 4 · 2H 2OAnthony et al , Handbook of Mineralogy (2001)