Three types of low-grade manganese ores belonging to the Pre-Cambrian age are found in the Bonai-Keonjhar belt of Odisha. Out of the siliceous, ferruginous and aluminous Mn-ores the later type was characterised mineralogically and subjected to different physical beneficiation methods such as gravity (heavy media separation, mineral separation and tabling) and magnetic separation. The results obtained for gravity separation was not very encouraging and the grade of Mn could not be improved beyond 30%. The magnetic separation method was quite useful and a product having only 23% Mn in the feed could be up-graded to more than 32% Mn. However, the increase in Mn-value is accompanied by concomitant rise in Fe value, which inhibits the direct use of the processed product but it can be suitably blended with low iron Mn-ores and finds good market value.

aluminous Mn-ore, magnetic separation, Bonai-Keonjhar belt