White, Blue, Yellow, Brown, Green, Brownish, Greenish, gray
White, Colorless, Blue, Red, Green, Yellow, Violet
Gemstones (2009), Flexible Flexible fragments.
Conchoidal, Conchoidal, Gemstones of the world (2001)
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)