UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
(Fe,Mn) 7Si 7O 21Ulrich Henn and Claudio C.
Ca 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)