Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
TiO 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 2(Ti,Fe)Si 4(O,F) 11Ulrich Henn and Claudio C.