Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
(Mg,Fe2+ ) 9(SiO 4) 4(F,OH)) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references