Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references