White, Colorless, Blue, Red, Green, Yellow, Violet
Colorless, Yellow, Blue, Reddish, Black, Reddish, Brown, Blue, gray, Black, Reddish, Brown, Blue, gray
Not Available
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
(Mg,Fe)Al 2O 4Gemdat.org , Management Team (2012)
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references