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