Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Uneven, Subconchoidal, Brittle, Metallic, Brittle, Metallic
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.
Zn 2(AsO 4)(OH)Michael OâDonoghue , Gems, Sixth edition (2006)