Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Uneven, Splintery, Conchoidal, Uneven, Splintery, Conchoidal, UnevenWalter Schumann, Gemstones of the world (2001)
Na 2(Ti,Fe)Si 4(O,F) 11Ulrich Henn and Claudio C.
SiO 2Arthur Thomas , Gemstones (2009)