Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Conchoidal, Brittle
Uneven, UnevenArthur Thomas, Gemstones (2009)
Fe 2O 3Arthur Thomas , Gemstones (2009)
Mg 3Si 4O 10(OH) 2Ulrich Henn and Claudio C.