Uneven, Uneven, Management Team (2012), Conchoidal, Brittle
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Fe 3O 4Ulrich Henn and Claudio C.
SiO 2(+Al 2O 3)Walter Schumann , Gemstones of the world (2001)