Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009)
SiCArthur Thomas , Gemstones (2009)
(Fe,Mn)Ta 2O 6Walter Schumann , Gemstones of the world (2001) More from other references