Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references