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