Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009)
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references