Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
Conchoidal, Conchoidal, Gemstones of the world (2001)
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references