Uneven, Uneven, Gemstones of the world (2001) More from other references
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
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Fe 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)