The film covers the second part of an, originally, three-part film on the Upper Harz ore mining industry, shot in 1923. This is a general survey of work in the central preparation plant at the Ottiliae shaft in Clausthal, where lead sulphide concentrates (PbS) and sulphide of zinc concentrates (ZnS) were won from the crude ores. Individual stages of the preparation of coarse, medium, and fine ores, and sediment, are shown in detail one after another. Size reduction machines used include coarse and fine jaw crushers, then coarse, medium, and fine roll crushers, and, finally, centrifugal grinders. Grading is done in revolving trommel screens and subsequent belt grading. Sorting is first done by hand selection (women and children), then in jiggers, on ascillating and percussion tables, and round buddles. The film closes with general shots of mining activity and ore analysis.