Irregular/uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009), Splintery
Na 2Ca 2Al 6Si 6O 24(CO 3) 2Walter Schumann , Gemstones of the world (2001) More from other references
Ca 2(Mg,Fe) 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.