Irregular/uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Na 2Ca 2Al 6Si 6O 24(CO 3) 2Walter Schumann , Gemstones of the world (2001) More from other references
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.