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