Abstract: A process for removing sulfur from sulfide-bearing ores by reacting water vapor with the sulfide-bearing ore forming hydrogen sulfide while simultaneously regenerating water vapor by reacting the hydrogen sulfide with lime. Advantageously, the process occurs in the absence of a net consumption or production of gaseous species so that the process can be carried out in a closed system with respect to the gaseous species. Sulfide-bearing ores which can be treated using the process of this invention include sulfide-bearing ores of molybdenum, zinc, iron, mercury, and copper. Advantageously, the molybdenum oxide so produced from the sulfide-bearing ore of molybdenum can be reacted further with lime and water producing calcium molybdate and hydrogen. The chalcopyrite form of the sulfide-bearing ore of copper produces bornite and magnetite.