Mineralogy, Microstructure, and Chemical Composition of Goethites in Some Iron Ore Deposits of Orissa, India

The Joda-Barbil region of the Jamda-Koira valley is one of the most important sources of iron ores in India. The mineralogy, texture, and chemical composition of iron ore of the region have been analyzed to understand the presence of different types of goethite and their compositional variation with respect to Fe, Al2O3, SiO2, and P that are essential for upgrading the ores for iron and steel making. The iron ore samples have been investigated by optical microscopy, EPMA, XRD, and TG-DTA. The optical microscopy studies have indicated three dominant textural types of goethite, such as (a) colloform-banded vitreous, (b) massive vitreous, and (c) earthy or ochreous goethite. The vitreous goethite is hard and crystalline, whereas ochreous goethite is clayey and consists of ultrafine crystallites often intimately admixed with kaolinite and gibbsite. EPMA studies indicated that (a) ochreous and colloform-banded goethite contain more alumina compared to massive vitreous goethite and (b) colloform-banded goethite has higher phosphorus contents (P2O5: 0.90-2.25%).