The invention relates to a method for separating impurities out of slags, dusts, minerals, preparation residues of minerals or of recyclings or remaining substances, subsequently called feed stock. In order to save energy and reduce costs, the inventive method is characterized by the combination of the following features: melting the feed stock containing the impurities; forming a copper melt; bring the feed stock into contact with the copper melt while adding reducing agents, preferably coke and/or coal; vaporizing, if required, existing volatile compounds such as metal chlorides; reducing metals of the feed stock more noble than copper in the copper melt, and; forming a slag with constituents of the feed stock to be purified that is less noble than copper.