In contrast to modern tailings from froth flotation, little is known about historic tailings from gravity separation. However, they may be of economic interest due to their higher metal grades compared to modern tailings. As an example for these types of historic tailings, the inner structure, as well as the economic potential (Pb, Zn, Cu, Ag, Sb), of the old Bergwerkswohlfahrt mine waste dump in Germany were studied. The investigations focused on textural, geochemical, and mineralogical properties. For this purpose, an extensive drilling program was undertaken. The drill cores were subsequently analyzed with a laser-induced breakdown spectroscopy (LIBS) core scanner to obtain the detailed spatial distribution of potentially valuable elements. The fine-sized residues could be differentiated into different layers, all of them including valuable metals in varying proportions. The strong variations in stratification and in metal distribution over short distances are caused by the batch-wise deposition of the tailings. This heterogeneity within short distances has to be taken into account for future exploration of these types of deposits. The application of a core scanner using LIBS is very convenient for detailed spatial analysis of drill cores, however, the calibration effort, particularly for heterogeneous sample material, is proportionally large. The valuable metal content for Bergwerkswohlfahrt was estimated to be 8000 metric tons of Pb and 610,000 ounces of Ag. Although of limited economic value, recycling might finance future remediation costs. Furthermore, the occurrence of historic tailings in nearby clusters may present further recycling opportunities.
Characterization and Economic Potential of Historic Tailings from Gravity Separation: Implications from a Mine Waste Dump (Pb-Ag) in the Harz Mountains Mining District, Germany
