Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)
Fe 2O 3Arthur Thomas , Gemstones (2009)