Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.