UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
Uneven, Conchoidal, Brittle, Metallic, ConchoidalArthur Thomas, Gemstones (2009)
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
Ca 3Cr 2(SiO 4) 3Ulrich Henn and Claudio C.