ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
(Al,Mg) 8(Al,Si) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al2SiO4(F,OH)2