ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
SiO 2Walter Schumann , Gemstones of the world (2001)
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.