UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)