Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Splintery
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.
Na 4Al 3Si 9O 24Cl to Ca 4Al 6Si 6O 24(CO 3,SO 4)Walter Schumann , Gemstones of the world (2001) More from other references