Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Fe 2SiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)