Gems, Sixth Edition (2006)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Metallic
SiO2 (with a high level of nickel impurities )
Mn2+ Zn 2SiO 4(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references