White, Colorless, Blue, Red, Green, Yellow, Violet
White, Green, Blue, Yellow, Brownish, Red, Blue, gray, Yellow, White
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Irregular
SiO 2 + H 2OUlrich Henn and Claudio C.
Mg(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)