Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references