Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Irregular/uneven, UnevenAnthony et al, Handbook of mineralogy (2001), Brittle, Uneven
BaSO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaAl 2Si 3O 10 · 3H 2OUlrich Henn and Claudio C.