Beneficiation of low grade Manganese ore from Siljora, Keonjhar District, Orissa

A low grade manganese ore from Siljora, Keonjhar District, Orissa, assayed Mn, 37.55%; MnO2,56.62; Fe, 12.46; SiO2, 7.56; Al2O3, 6.45; and P,0.086 percent. The manganese minerals were psilomelane, pyrolusite and magnetic. The principal gangue minerals were hydrous iron oxides with some hematite. Straight magnetic separation did not produce a satisfactory grade of manganese concentrate. Reduction roast of the un-washed ore at -3mesh size followed by magnetic separation at -14 mesh gave a manganese concentrates assaying 50.8% Mn (Mn/Fe ratio 7:1) with a recovery of about 90 % Mn. Magnetic separation at -35 mesh after reduction roast slightly improved the grade of concentrate to 51.6% Mn (Mn/Fe ratio 7:1) with almost the same recovery (about 90.5% Mn). The grade of concentrate further improved to 53.0% % Mn (Mn/Fe ratio 7:1) but the recovery dropped to about 85.7% % Mn. When washed ore was used for reduction roast.