Investigation of ancient iron and copper production remains from Irtyash Lake (middle Trans-Urals, Russia)

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In the mountain-forest zone of the middle Trans-Urals, iron technology is conventionally thought to have been adopted during the local early Iron Age (EIA, 7th-3rd c. BCE) by the skilled bronze-working population of the Itkul culture. However, these claims remain unresolved at present, as most of excavations of Itkul sites were carried out during 1960–1980′ s, and some Itkul sites featuring iron production remains also contain evidence of medieval (6th-10th/16th c. AD) occupation. We analyse via SEM-EDS iron-metallurgical slags, iron ores, technical ceramics, iron object and copper slags from one of the key clusters of Itkul sites, Irtyash Lake, in order to provide first insight into past metal production practices, exploited ore sources and the possible link between copper and iron metallurgy in this part of the Urals. The results confirm bloomery smelting of local ironstone ores in Irtyash area, at least during the medieval period. Beyond that, the analyses provide the first evidence for small-scale iron-smithing at the EIA sites of Irtyash-1 and Shatanov-5, alongside secondary copper-working activities. The compositional similarity observed between iron- and copper-working slags from Irtyash-1 indicates the deliberate use of talc-tempered clay mixtures for iron and copper-metallurgical ceramics, which is likely related to their refractory properties. The iron-working slags from the EIA sites suggest the use of iron ores associated with copper deposits, although primary slags formed during the smelting of these iron ores were not identified. It is possible that the early trials iron metallurgy in the middle Trans-Urals, during the EIA, were stimulated by the rich experience of the Itkul population with copper metallurgy and their deep knowledge of the diverse mineral resource base of the Urals.