Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.