Adding oxygen to the air in the gas desulfurizing process results in a number of benefits, e.g. increased plant capacity, more flexibility, and improved conversion of ammonia. By using oxygen to convert mineral sulphides to sulphates and processing them, gold yield can be more than doubled over standard ore gravity separation and concentration. By sparging 94-95% oxygen into a thickened flotation concentrate (which has been heated under pressure) an oxidized slurry results. Not only are sulphides converted to sulphates by the O2, but arsenic is converted to ferric arsenate.