Uneven, Conchoidal, UnevenArthur Thomas, Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Fe2+ CO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references