Natural magnetite and hematite samples taken from iron ore deposits associated with Precambrian banded iron-formation (BIF) at Ari Dongri (20°23′N:81°3°E), Bastar district in Central India have been studied by Mossbauer, XRD and positron annihilation techniques. Three magnetite samples show a genetic association with α-Fe2O3 with a wide range of variations in Fe3O4:α-Fe2O3 ratio. The fourth sample, a typical specular hematite, shows α-Fe2O3 content of the order of 90%, the rest being magnetite. The magnetite present in the samples was found to be stoichiometric. None of the samples contains maghemite (γ-Fe2O3). Some geological implications of the observed variation in the oxidation states of the samples are considered.
Volume 43, 2020
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