Abstract: Sulphide and sulphosalt mineralization in the Hällefors silver mining district occurs as stratabound bodies in skarn-like black carbonates and other carbonates in the eastern part of the district, and as epigenetic, tectonically controlled vein mineralization in tuffaceous metavolcanics and, to a lesser extent in slates, in the western part.

Previous work has suggested that the Ag-bearing Hällefors deposits were formed by the action of metamorphic solutions on sediments of volcano-sedimentary origin. At the stages of sulphosalt and sulphide formation, temperature and pressure conditions were probably in the ranges 500–440 K and 4.5–3.5 kbar. Examination of a log a_S2-1/T diagram and of Ag-Sb phase relations combined with study of the ores suggest the paragenesis of the Ag-bearing minerals is as follows: allargentum and dyscrasite as exsolution bodies in silver bearing galena; Ag-containing tetrahedrite → freibergite → miargyrite → pyrargyrite → stephanite (from hydrothermal solutions).