Size Classification vs. Mineral Distribution and Its Implication in Optimum Utilization of Khondalite-Hosted Bauxite Ore from Eastern India

Abstract

Three typical litho-types such as ‘saprolite,’ ‘bauxite’ and ‘laterite/lateritic ore’ from different levels of khondalite-hosted bauxite profile of Baphlimali plateau, Rayagada district, Odisha, Eastern India, have been studied. Mineralogical variations between different size fractions are interpreted for their optimum utilization. Mineralogy of individual bulk and its respective classified fractions are established from their XRD, DTA and TGA patterns. The saprolite, present in the lower most level of the profile, is rich in aluminum silicate (kaolinite), does not find use in alumina refinery and is usually considered as waste. However, if it is size-classified, the − 2.0 + 0.50 mm fraction, measuring over 21% by volume of the bulk, is found to contain substantial amount of gibbsite that can be separated and utilized for alumina recovery. The bauxite, present at the intermediate level of the profile, is rich in aluminum hydroxide (gibbsite). However, sometimes it contains hematite as major impurities (Fe ~ 10%). Though such ore is of metallurgical grade, around 26 vol% of the ore can be used for refractory purpose by simple separation of < 0.15 mm fraction. The ‘laterite,’ present in the upper most level of the profile, constitutes a mixture of gibbsite, kaolinite, hematite/goethite. Though its Fe-content is within permissible limit, the reactive silica contributed by kaolinite inhibits its use in alumina refinery. However, separation of − 2.0 + 0.25 mm size fraction from the bulk, amounting to 42% by volume, reduces kaolinite content appreciably. The study thus demonstrates that by simple size classification, different litho-types from a bauxite profile can be optimally utilized.