Uneven, Subconchoidal, Uneven, Subconchoidal, Splintery, UnevenArthur Thomas, Gemstones (2009)
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
Al 2SiO 5Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references