Mine waste: Nuisance or important metal resource for the future?

Germany has a long history in metal ore mining stretching over a period of more than 1000 years. Both small and large heaps or dumps remain in the mining districts typically without any safety measures (coverage, monitoring etc.). Often these sites are still a considerable point source for pollutants like metals, metalloids or processing chemicals. However, extraction technologies have been much less effective in the past and for certain elements (e.g. Ge) no technical application has been known. As such, mine waste including historic waste or ore dumps and tailings may represent a considerable and easily extractable future resource especially for technology critical elements.

We investigate the mineralogy, geochemistry and leaching behaviour of different types of mine residues in former mining districts of the Black Forest, Wiesloch and the Donnersberg area. With respect to the critical raw materials Ge, Sb, barite and fluorite, several of the investigated mine waste seem to be of potential economic interest. But elements like Pb, Zn (both in the wt% range) or Ag (>100 mg/kg) are also promising with regard to reprocessing in some of the investigated districts. From an environmental point of view, Pb, Zn, As, Cd, Sb und Tl are of concern regarding their concentration and leachability. Both, the content and potential mobility largely depend on the ore type, the period of extraction and the processing technique applied. We think that extracting raw materials from mine residues has the advantage of gaining metals locally and giving back space to nature and society at the same time.