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