Uneven, Brittle, Metallic, Gemstones (2009)
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Na 2[Al 2Si 3O 10] · 2H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.