Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Gemstones (2009), Flexible Flexible fragments.
(Be,Cs) 3Al 2Si 6O 18 · 0.5H 2OUlrich Henn and Claudio C.
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references