Colorless, White, Brownish, Reddish, Black, Brownish, Black, Colorless, gray, White, Reddish, Brown
Green, Green, Yellow, Brown, White, gray, Black
Uneven
Splintery, Granular, Splintery, Granular, Gemstones (2009)
Na 3AlF 6Ulrich Henn and Claudio C.
Ca 2(Mg,Fe) 5(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references