Wet methods of producing Mn or MnO2 from low grade Mn ores containing much Fe has been studied. While the hitherto known processes such as the sulphurous acid leaching or the reducing roasting-sulphuric acid leaching processes have the disadvantage of dissolving much Fe side by side with Mn, the present roasting process which is based upon the preferential sulphatizing of Mn makes practically no Fe go into solution. The process has the additional merit of making use of the pyrrhotite to greater advantage than the pyrite as an admixture in the roasting procedure.