Splintery, UnevenArthur Thomas, Difficult, Fibrous
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
NaAlSi 2O 6Ulrich Henn and Claudio C.
Mg 3B 7O 13ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references