Uneven, Subconchoidal, Uneven, Subconchoidal, Splintery, UnevenArthur Thomas, Gemstones (2009)
Gems, Sixth Edition (2006)
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
SiO2 (with a high level of nickel impurities )