Colorless, Yellow, Blue, Reddish, Black, Reddish, Brown, Blue, gray, Black, Reddish, Brown, Blue, gray
Yellow, Green, Blue, Violet
Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
Not Available
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
Al 2O 3Ulrich Henn and Claudio C.