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