White, Colorless, Blue, Red, Green, Yellow, Violet
White, Colorless, Blue, Red, Green, Yellow, Violet
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Not Available
SiO 2Ulrich Henn and Claudio C.
SiO 2 (with trace Cr minerals) Gemdat.org , Management Team (2012)