Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009)
CuSMichael OâDonoghue , Gems, Sixth edition (2006) More from other references
MnTa 2O 6Walter Schumann , Gemstones of the world (2001) More from other references