ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Subconchoidal, Uneven, Subconchoidal, Splintery, UnevenArthur Thomas, Gemstones (2009)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references