Uneven, Brittle, Metallic
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009)
(K,Na) 3(Fe2+ ,Mn) 7Ti 2Si 8O 24(O,OH) 7Anthony et al , Handbook of mineralogy (2001)
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references