Detrital Glass Provides Evidence of Leaded-Bronze Refinement at Ancient Placer Tin Mining Sites in Serbia

Archaeological evidence for prehistoric placer tin mining is rare due to the ephemeral nature of the workings and the associated tools in the dynamic setting of active river systems. Here, we report an additional line of evidence for metallurgical activities at stream tin mining in Serbia at Mt. Cer and Bukulja. Rivers at these locations contain Pb-rich-glass grains, many of which are also enriched in Cu and Sn. Compositionally, the detrital grains of glass are similar to the vitreous infillings on a bleached ceramic sherd found at Spasovine, an archaeological site situated on the bank of the tin-rich Milinska River. The high-Pb-bearing (average 42 wt%) and Sn-bearing (average 0.7 wt%) composition of the glass, along with the inclusions of secondary cassiterite, indicate that the slag was derived from the refinement of leaded bronze (i.e., lead removal). Although the detrital glass slag grains lack direct archaeological context, broader archaeological observations limit their production to either the Roman or Medieval Periods. The presence of Pb-Cu-Sn metallurgical glass grains in a river at Bukulja provides the first concrete evidence of prehistoric tin mining at this locality, which demonstrates that sluicing for crushed glassy residues is a viable means to prospect for as yet undiscovered sites of ancient metallurgical activities.