In new research, archaeologists examined a round heavy metal object from Särdal in the west Swedish region of Halland. Due to its shape and size, it seemed to the researchers a Bronze Age artifact, but the object turned out to be made of a copper-zinc-tin-lead alloy, typical of the Iron Age and later periods.
The plano-convex ingot from Särdal, Halland, Sweden. Image credit: Sabatini et al., doi: 10.1016/j.jasrep.2025.105312.
The ancient ingot was found in the autumn of 2022 at the village of Särdal along the west coast of Sweden.
The artifact proved to be a so-called plano-convex ingot — the first of its kind ever found in the country.
“The plano-convex ingots, often also called ‘bun’ ingots or ‘casting cakes,’ are common throughout the Bronze and Iron Age, but vary in size, shape, and composition,” said University of Gothenburg researcher Serena Sabatini and colleagues.
“They are round artifacts with a generally flat upper face or topside and a variously bulged convex bottom or underside.”
“They are manufactured by pouring the melted metal into a mould or in a shallow cavity in the ground.”
“Most of those ingots have a ‘bubbly’ and rough upper face, confirming that the metal was poured in an open casting mould, while the underside is generally smooth as it was not in contact with air during production.”
“Being a relatively simple product, they are widely spread across Eurasia and have been used not only in prehistoric but also in historical times.”
The Särdal ingot is 14-15.3 cm in diameter, around 2.5 cm thick, and weighs 1223.5 grams.
The surface of the ingot shows significant traces of corrosion especially on the rougher surface of its upside.
The overall shape, size, and weight of the ingot strongly suggested that it could be a Bronze Age find.
“Initially, we believed the Särdal ingot to date back to the Bronze Age,” the archaeologists said.
“However, as it was found alone and could not be dated by its archaeological context, we decided to run isotopic and chemical analyses to determine its composition and suggest a possible chronology.”
The analyses provided unexpected results as the ingot turned out to be made of a copper-zinc-tin-lead alloy that was typical of the Iron Age and later periods.
“Once the results arrived, and thanks to the open character of the international scientific community of scholars working with archaeometallurgical issues in the past, we realized that the isotopic and elemental characteristics of the Särdal ingot were very close to a group of artifacts from two possible hoards found in the Iława Lakeland region, in northeastern Poland,” the researchers said.
Studies from the Baltic regions, which were intensely networking with West Sweden and southern Scandinavia during the pre-Roman Iron Age, indicate that the alloy of the type from Särdal and the Iława Lakeland was present in the area already during the second half of the 1st millennium BCE.
“We propose therefore that the plano-convex ingot from Halland and the rod ingots from Poland can be both considered the outcome of maritime trade in metal connecting Scandinavia and the Baltic Sea to the Iberian Peninsula during the period corresponding to the Scandinavian pre-Roman Iron Age, following ancient routes in use since the Late Bronze Age,” the authors concluded.
Their paper will appear in the October 2025 issue of the Journal of Archaeological Science: Reports.
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Serena Sabatini et al. 2025. Iron age metal trade between the Atlantic and the Baltic Sea: new insights from the first complete plano-convex ingot found in Sweden and ingot rods from the Iława Lakeland in northeastern Poland. Journal of Archaeological Science: Reports 66: 105312; doi: 10.1016/j.jasrep.2025.105312