Uneven, Subconchoidal, Uneven, Subconchoidal, Splintery, UnevenArthur Thomas, Gemstones (2009)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references