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