White, Colorless, Blue, Red, Green, Yellow, Violet
Colorless, Greenish, Colorless, Green, gray, Yellow
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
Ca 2Al 3(SiO 4) 3(OH)Walter Schumann , Gemstones of the world (2001) More from other references