A complete plano-convex ingot has been uncovered in Sweden for the first time. When researchers at the University of Gothenburg analyzed the object using isotopic and chemical methods, the results were surprising. “Due, in particular, to its shape and size, it seemed to us a Bronze Age artifact, but the ingot turned out to be made of a copper-zinc-tin-lead alloy, typical of the Iron Age and later periods,” says Serena Sabatini.
Plano-convex ingots are most often made of copper, although some are formed from bronze or other copper-based alloys. They are frequently found in regions around the Mediterranean, as well as across continental Europe and along the Atlantic seaboard. Historically, these rounded ingots served as a practical way to transport metal during both the Bronze Age and the Iron Age.
Reevaluating the Särdal Find
At first, archaeologists from the University of Gothenburg assumed the Särdal ingot belonged to the Bronze Age. Because it was recovered on its own and lacked any material that could help assign a date, the team turned to scientific testing to understand what it was made of and to estimate when it might have been produced.
Their analyses overturned the initial assumption. The composition matched a copper-zinc-tin-lead alloy characteristic of the Iron Age and later periods.
Collaboration Reveals Wider Connections
“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,” says Serena Sabatini.
According to the researchers, this case demonstrates that even isolated artifacts, which are often challenging to interpret, can gain meaningful historical context through careful study. Bringing together archaeological approaches with scientific analyses can turn a single, enigmatic object into evidence that contributes to a broader understanding of the past.
“Networking and international collaboration are also important to unveil patterns and data that would remain unknown when one look 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!” says Serena Sabatini.
Applying Established Archaeometallurgical Techniques
The research team used well-established techniques in archaeometallurgy (which is the branch of archaeology specialized in the study of ancient metals), including lead isotope and trace element analyses of metal artifacts. These analytical methods have been employed since the 1980s to study both the composition and the likely geological sources of metal (in the sense that they enable to point out the minerary region from which the metal was extracted).
“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 in northeastern Poland. Given the astonishing similarity of the metal composition in all those artifacts we also manage to strengthen earlier hypotheses about contacts and networking in the Baltic area during the Nordic pre-Roman Iron Age,” says Serena Sabatini.
The study is published in Journal of Archaeological Science.