UnevenArthur Thomas, Gemstones (2009) Tough, UnevenArthur Thomas, Gemstones (2009) Tough, Brittle, Uneven
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Mn 8Si 6O 15(OH,Cl) 10Ulrich Henn and Claudio C.
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.