Beneficiation of a Ferruginous Manganese ore from Nagri-Joida, North Kanara, Bombay

A low-grade ferruginous manganese ore sample from Nagri-Joida in Suplapeta, North Kanara assayed 33.3% Mn, 19.6% Fe, 3.2% SiO2, 4.01% Al2O3 and 0.02% P. The manganese minerals were chiefly psilomelane and a little pyrolusite. The primary gangue was limonitic ochre. Alumina was present mostly as laterite. Neither flotation nor straight magnetic separation gave satisfactory results. Roasting of the ore in a reducing atmosphere converted the iron-bearing minerals into magnetite, which was separated magnetically from the manganese minerals (reduced but nonmagnetic) concentrates assaying about 56% Mn and 6% Fe were obtained with a recovery of about 70% manganese. Higher recoveries up to 83% Mn are possible, for slightly lower grades of concentrates (54.2% Mn and 8% Fe) within the required specification. The magnetic products which would contain some manganese may also prove service-able as manganiferous iron ore.