White, Colorless, Blue, Red, Green, Yellow, Violet
Reddish, Greenish, White, Red, Yellow, Green, Grey, Blue, Brown, Colorless, gray, orange
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
CaCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references