Mossbauer, XRD and positron annihilation studies on natural magnetite and hematite ore from Ari Dongri, central India

Abstract

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 a-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.