Conchoidal, Metallic, UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Splintery, UnevenArthur Thomas, Difficult, Fibrous
Cu 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
NaAlSi 2O 6Ulrich Henn and Claudio C.