Beneficiation of a Ferruginous Manganese ore (‘D’ Grade) from Nagri-Joida, N. Kanara

A low-grade ferruginous manganese ore (marked ‘D’grade) received from Nagri-Joida, North Kanara, assayed 34.71% Mn, 18.49% Fe, 0.03% P, 3.93% SiO2 and 6.7% Al2O3. Psilomelane was the principal manganese mineral present with some pyrolusite. The primary gangue was limonitic ochre. Alumina was present, mostly as laterite . Magnetite, quartz and clay were in minor amounts. Straight magnetite separation after heating the sample did not produce a satisfactory grade of manganese concentrate. Reduction of the ore at 500-560 ° C followed by crushing the material to -20 mesh and magnetic separation yielded manganese concentrates assaying between 52.1 and 55.5 percent Mn with recoveries varying from 87.0 to 78.5% Mn and with Mn:Fe between 6:1 and 9:1.