A method of oxidizing carbonaceous ores to assist in the recovery of metals is provided. The method includes the steps of heating a bed of carbonaceous ore in the reaction chamber of a reactor vessel, using microwave energy to initiate and sustain oxidation of the carbonaceous ore within the bed into carbon dioxide, controlling the inflow of oxygen into the reaction chamber to provide sufficient oxygen to maintain the reaction C+O.sub.2.dbd.CO.sub.2, and monitoring the depletion of carbon from the carbonaceous ore.