White, Colorless, Blue, Red, Green, Yellow, Violet
White, Blue, Yellow, Brown, Green, Brownish, Greenish, gray
SiO 2 (with trace Cr minerals) Gemdat.org , Management Team (2012)
Al 2Si 4O 10(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references