Researchers in Sweden have analyzed a rare plano-convex ingot discovered in Särdal, initially thought to be from the Bronze Age but now confirmed as an Iron Age artifact. The object's copper-zinc-tin-lead alloy matches similar finds in Poland, suggesting extensive trade networks across the Baltic region. This discovery highlights the value of scientific collaboration in reshaping understandings of ancient history.
In a breakthrough for archaeometallurgy, a complete plano-convex ingot was unearthed in Särdal, Sweden, marking the first such find in the country. Initially, experts from the University of Gothenburg believed the artifact dated to the Bronze Age due to its distinctive shape and size. However, advanced isotopic and chemical analyses revealed it was composed of a copper-zinc-tin-lead alloy, characteristic of the Iron Age and subsequent periods.
Plano-convex ingots, typically made from copper or bronze alloys, were practical for transporting metal across regions like the Mediterranean, continental Europe, and the Atlantic seaboard during both the Bronze and Iron Ages. Without accompanying materials to provide a clear timeline, the team relied on scientific methods to pinpoint its origins.
The results prompted collaboration with Polish researchers studying Iron Age artifacts from the Iława Lakeland in northeastern Poland. The compositions proved nearly identical, strengthening evidence of long-distance exchanges in the Nordic pre-Roman Iron Age. "Thanks to the collaborative climate of the archaeometallurgy research world—we teamed up with a group of Polish scholars, who were working with some Iron Age finds which have the almost exact composition of our ingot," explained Serena Sabatini, a lead researcher.
This work underscores how isolated objects can illuminate broader historical patterns through interdisciplinary approaches. Established techniques, such as lead isotope and trace element analyses—developed since the 1980s—helped trace the metal's geological sources and propose a contextual framework. "What is new in this study is that we went a step further, and by combining the obtained data with known historical and archaeological information, we managed to propose a historical context for both the unique Särdal plano-convex ingot and the rod ingots from the Iława Lakeland area," Sabatini noted.
Sabatini emphasized the role of international teamwork: "Networking and international collaboration are also important to unveil patterns and data that would remain unknown when one looks exclusively at the local context. This work clearly shows the importance of teamwork and data sharing. Without the successful collaboration with our Polish colleagues, we would have never achieved such remarkable results!"
The findings appear in the Journal of Archaeological Science: Reports (2025, volume 66, article 105312).