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