Abstract: Finely pulverized facing sand particles are provided for the production of casting molds in metal foundries. A feed device passes a bed of molding sand containing lumps to a refining device. The refining device includes a plurality of refining elements on a carrier. The refining elements are movable along an orbital path to remove lump-free facing sand particles from the bed of sand and deliver these in a free falling stream of finely pulverized facing sand particles. The refining elements are spaced on the carrier and the carrier is moved at a speed to maintain the spaces free of lumps.