Blue
Colorless, Colorless, Violet, White
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)
Ca 3Al 2(SO 4)(F,OH) 10Ulrich Henn and Claudio C.