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.
(Ca,Mg,Mn)SiO 3Gemdat.org , Management Team (2012)