UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
(Fe,Mn) 7Si 7O 21Ulrich Henn and Claudio C.
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.