Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
ConchoidalArthur Thomas, Gemstones (2009)
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.
MnTa 2O 6Walter Schumann , Gemstones of the world (2001) More from other references