New evidence on Iron Age bronze metallurgy in southwestern Iberian Peninsula: ingots and artefacts from Cabeço Redondo (Portugal)

Archaeological works at Cabeço Redondo (southern Portugal), located in the Guadiana River basin, identified the remains of a monumental building with an architecture, ceramics and metal artefacts in line with post-Orientalizing contexts of the sixth–fifth century BC in southwestern Iberian Peninsula. Metal debris connected to the copper-based metallurgy include a significant collection of ingots, lumps and small prills, with emphasis to a massive plano-convex ingot, while artefacts comprise tools, small implements, ornaments and rods. A chemical and microstructural study involving micro-EDXRF, optical microscopy and SEM–EDS provided some answers about foundry activities and identified the composition and post-casting manufacture of artefacts. Most metal debris were composed of pure copper (> 99 wt% Cu), although some examples attest the use of bronze and leaded bronze at Cabeço Redondo metallurgical workshop. Apart from a few copper items, the artefact collection mainly shows low-tin bronze alloys (7.6 ± 3.9 wt% Sn) and leaded bronze alloys (7.7 ± 4.4 wt% Sn and 6.0 ± 3.4 wt% Pb). The manufacture of copper and binary bronze artefacts included hammering and annealing, while leaded bronzes were usually not subjected to post-casting work, implying a well-defined relation among function, composition and manufacture. The features of metal debris and artefacts were then compared with the ones of coeval sites of this region to integrate the metallurgical evidence of Cabeço Redondo into the technological pattern of southwestern Iberian Peninsula during the middle of the first millennium BC.