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