Tracking silver in the Lappberget Zn-Pb-Ag-(Cu-Au) deposit, Garpenberg mine, Sweden: Towards a geometallurgical approach

Abstract

The complex mineralogy and low concentration of silver in polymetallic ores makes mineralogical characterization and extraction challenging. In this study, quantified mineralogical characterization of the flotation products from batch flotation tests was undertaken for a silver-rich zinc-lead ore using QEMSCAN® (Quantitative Evaluation of Minerals by Scanning Electron Microscope), scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). Ten major silver minerals were identified and their behavior during flotation was discussed based on their different mineralogical and textural characteristics. Results from this study also showed the variability in the composition of some silver minerals (e.g., tetrahedrite and electrum), the presence of structurally bound silver in galena, and the formation of sulfur-based silver coating on chalcopyrite, galena, and tetrahedrite. A metallurgical balance generated using the QEMSCAN® data shows a very strong linear correlation (R2 = 0.99) against the chemical assay derived using inductively coupled plasma mass spectrometry (ICP-MS). This suggests that the quantification of mineralogical data produced using automated mineralogy is possible even for tracking trace minerals. The effectiveness of this methodology lies upon the creation of a robust mineral library based on a comprehensive mineralogical study, which can be used for tracking of by-product metals during the flotation of complex ores.