Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.
Fe 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)