A metal ingot found decades ago on Sweden’s west coast has been reclassified as an Iron Age artifact after chemical and isotopic analyses overturned long-standing assumptions about its age. The plano-convex ingot – Sweden’s first complete example – was initially thought to be Bronze Age based on its form alone. But its copper–zinc–tin–lead composition aligns instead with Iron Age alloys, revealing that the object belongs to a later and historically important metallurgical tradition.
“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,” said Serena Sabatini of the University of Gothenburg, in a press release. This reclassification matters because plano-convex ingots are usually linked to established metal-exchange systems in Europe – systems whose presence in Scandinavia has been suggested but rarely evidenced by complete objects.
The researchers used established archaeometallurgical tools – including lead isotope and trace-element analysis – to compare the Swedish ingot with rod-shaped ingots from the Iława Lakeland in northeastern Poland. The alloys showed “almost exact” compositional matches, Sabatini notes, strengthening earlier hypotheses that Iron Age communities around the Baltic were linked through shared networks of exchange. Lead isotope ratios further point to metal extracted from southwestern Iberian ore fields, indicating that long-distance connections reached well beyond northern Europe.
“Thanks to the collaborative climate of the archaeometallurgy research world – we teamed up with a group of Polish scholars. Without the successful collaboration with our Polish colleagues, we would have never achieved such remarkable results!” Sabatini said.
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