Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Uneven
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.
ThCa 2Si 8O 20Walter Schumann , Gemstones of the world (2001) More from other references