Uneven, UnevenArthur Thomas, Gemstones (2009)
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Cu 5(SiO 3) 4(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 3(Na,K)Al 4Si 4O 16Ulrich Henn and Claudio C.