Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
CuSMichael OâDonoghue , Gems, Sixth edition (2006) More from other references
(Ca,Mg,Mn)SiO 3Gemdat.org , Management Team (2012)