White, Colorless, Blue, Red, Green, Yellow, Violet
Colorless, White, gray, Brownish, Greenish
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Micaceous, Brittle
SiO 2 + H 2OUlrich Henn and Claudio C.
KAl 2AlSi 3O 10(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references