Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Splintery, Granular, Splintery, Granular, Gemstones (2009)
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.
Ca 2(Mg,Fe) 5(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references