UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
(Fe,Mn) 7Si 7O 21Ulrich Henn and Claudio C.
(Mg,Fe) 5(SiO 4) 2(F,OH) 2Ulrich Henn and Claudio C.