Blue, White, Grey, Yellow, Green, Colorless, Red, gray
White, Blue, Yellow, Brown, Green, Brownish, Greenish, gray
Uneven, Conchoidal, Brittle
Gemstones (2009), Flexible Flexible fragments.
(Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references