Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Gemstones (2009), Flexible Flexible fragments.
Na 3(Na,K)Al 4Si 4O 16Ulrich Henn and Claudio C.
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references