Uneven, UnevenArthur Thomas, Gemstones (2009), Brittle
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
MnPO 4Walter Schumann , Gemstones of the world (2001) More from other references
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references