Medieval Pb (Cu-Ag) Smelting in the Colline Metallifere District (Tuscany, Italy): Slag Heterogeneity as a Tracer of Ore Provenance and Technological Process

Archaeological investigations of the Colline Metallifere district (Southern Tuscany, Italy) have highlighted several Medieval sites located close to main Cu-Pb-Fe (Ag) ore occurrences. This study is focused on investigation late-medieval slags from Cugnano and Montieri using both geochemical mineralogical methods understand slag heterogeneities as result differences technological processes. Matte-rich present in (with abundant matte ± speiss frequent relict phases) represent waste products related primary sulphide smelting obtain a raw lead bullion. The distribution between Ca-rich or Fe-rich dominant composition, consequent mineralogy, are tracers different ore–gangue association that occurred two sites. Silver only very small matte-rich ores enclosed within mortar site; wastes derived silver-rich mineral charges were probably crushed for recovery silver. Matte-poor found at second smelting; bullion obtained (both Fe- Ca-rich) was re-smelted, adding silica Al2O3-phase-rich fluxes, under more oxidizing conditions reduce metal impurities. step employed Zn-rich ores; this process helped segregate zinc improve quality metal.