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