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Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by X-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods
Hiraga, R.; Gomes, O.F.M.; Neumann, R. Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by Χ-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods. Minerals2021, 11, 346.
Hiraga, R.; Gomes, O.F.M.; Neumann, R. Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by Χ-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods. Minerals 2021, 11, 346.
Hiraga, R.; Gomes, O.F.M.; Neumann, R. Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by Χ-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods. Minerals2021, 11, 346.
Hiraga, R.; Gomes, O.F.M.; Neumann, R. Maghemite in Brazilian Iron Ores: Quantification of the Magnetite-Maghemite Isomorphic Series by Χ-ray Diffraction and the Rietveld Method, and Confirmation by Independent Methods. Minerals 2021, 11, 346.
Abstract
Maghemite (γ-Fe2O3) is a mineral formed from magnetite oxidation at low temperatures, an intermediate metastable term of the magnetite to hematite oxidation and could be mixed with both. It has magnetic susceptibility similar to magnetite, crystal structure close to magnetite with which it forms a solid solution, while compositionally it equals hematite. Maghemite is thus easily misidentified as magnetite by X-ray diffraction and/or as hematite by spot chemical analysis in iron ore characterization routines. Nonstoichiometric magnetite could be quantified in samples of Brazilian soils and iron ores by the Rietveld method using a constrained refinement of the X-ray patterns. The results were confirmed by reflected light microscopy and Raman spectroscopy, thus qualitatively validating the method. X-ray diffraction with the refinement of the isomorphic substitution of Fe2+ by Fe3+ along the magnetite-maghemite solid solution could help to suitably characterize maghemite in iron ores, allowing for the evaluation of its ultimate influence on mineral processing, by affecting its surface and breakage properties.
Keywords
Iron ore; Maghemite; Nonstoichiometric magnetite; X-Ray diffraction; Ore characterization
Subject
Environmental and Earth Sciences, Atmospheric Science and Meteorology
Copyright:
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