Low grade manganese ore from West-Central Sinai consists mainly of pyrolusite and hematite with minor amounts of psilomelane and barite. Manganese dioxide does not dissolve in sulfuric acid under atmospheric pressure, but rapidly dissolves under oxygen pressure in an autoclave in presence of pyrite. Pyrite is oxidized to ferrous sulfate and sufluric acid which in turn dissolves manganese dioxide to manganese sulfate. This pressure leaching process was systematically studied. Almost complete extraction of manganese was achieved at temperature 220°C under oxygen pressure of 15 bar after 30 minutes of leaching and at MnO₂/FeS₂ molecular weight ratio equal 1.0. The residue is encriched in iron so that it could be used to produce feed stock for iron smelting.