Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Fe 2O 3Arthur Thomas , Gemstones (2009)
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)