ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
Na 2(Ti,Fe)Si 4(O,F) 11Ulrich Henn and Claudio C.