Uneven, Uneven, Gemstones of the world (2001) More from other references
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Ca 10Mg 2Al 4(SiO 4) 5(Si 2O 7) 2(OH) 4Ulrich Henn and Claudio C.
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.