Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.
Fe 2O 3Arthur Thomas , Gemstones (2009)