Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
KAlSi 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 3(Na,K)Al 4Si 4O 16Ulrich Henn and Claudio C.