Not only in Germany there are hundreds of tailings originating from the closed mining. Some of these secondary deposits are likely to contain valuable residues that could be exploited economically today. In order to be able to develop these, however, new technologies often have to be developed first. The Earth System Knowledge Platform of the Helmholtz Society provides information about this problem area (see https://www.eskp.de/energiewende-umwelt/sekundaere-rohstoffquellen-altlast-rohstoff-oder-kulturelles-erbe-9351013/). A general description of the problem can be found under https://www.sciencedirect.com/science/article/abs/pii/S089268751730239X?via=ihub.