Beneficiation of low-grade Manganese ore from Marivalasa, Salur, Srikakulam District

Abstract

A low grade manganese ore assaying 28.63% Mn,12.68% Fe, 18.44% SiO2, 6.19% Al2O3 and 0.2% P was received from Marivalasa, Salur, Srikakulam district. The manganese minerals were oxide viz. psilomelane and pyrolusite with quartz, garnet and limonite (ochre) as the principal gangue minerals. Gravity separation or straight magnetic separation did not produce satisfactory grade of manganese concentrates. Reduction roast of the -4 mesh ore after attrition grinding to eliminate the soft ochre, followed by magnetic separation yielded a manganese concentrate assaying 47.1% Mn with a Mn/Fe ratio of 6.9 and with a recovery of 64.2%. Reduction of the -4+35 by magnetic separation at -20 mesh yielded manganese concentrates assaying from 50.10% Mn to 48.18% % Mn with recoveries varying from 47.7% to 71.6% Mn and with Mn:Fe ratios between 7.9:1 to 5.5:1. Phosphorus in the concentrate was over 0.21% which was even slightly higher than that in the original ore and hence the concentrate might require blending with other ores for production of ferro-manganese.