The study was published in the journal Antiquity. The mine is located near Granja de Torrehermosa in the province of Badajoz and consists of a copper ore outcrop about 300 meters long.
Systematic excavations at the site have been underway since 2020. According to the researchers, ancient miners dug a trench 2–4 meters wide along the ore vein, and drilling showed that the workings reached a depth of 7 to 16.5 meters.
Over time, the workings were completely filled in with rock debris. Concentrations of charcoal at the bottom of one of the trenches indicate that the ore was probably broken up with fire: when heated, the rock cracked.
Radiocarbon analysis of charcoal from the mining trench and the residential area yielded 17 dates that fall roughly within the period from 1300 to 800–700 BC. By comparison, only 11 Late Bronze Age dates from five sites had previously been known for all mines on the Iberian Peninsula, and only six mines in the region have been reliably attributed to this period.
Archaeologists also found 892 stone tools, including 735 hammers with a groove for attaching a handle. Near the workings, the remains of a circular hut were discovered, which the authors consider part of a seasonal miners' camp.
Copper droplets and about 300 kilograms of slag, according to the authors' estimate, show that metal was not only extracted here but also smelted, although some of the finds in the smelting area belong to the Roman and Islamic periods. The scientists estimate that over its entire lifetime the mine could have produced from 49 to 738 tons of copper.
This estimate is comparable to the largest prehistoric mine in Wales, Great Orme, where between 1600 and 1400 BC between 202 and 756 tons of copper were extracted, although Las Minillas is far behind the Austrian Mitterberg district, which produced about 23,000 tons of copper between 1700 and 1300 BC. To understand where the metal went, the researchers compared lead isotopes and the chemical composition of the ore, slags, and copper droplets with data on more than 300 Bronze Age bronze objects from Scandinavia and found matches with 11 items, seven of which date to 900–700 BC.
A preliminary comparison also showed matches with some bronze objects from Britain, Poland, Spain, and Portugal. The authors consider Las Minillas part of a network of more than 100 ancient mines in the south of the Iberian Peninsula and suggest that southern Iberian copper may have been transported by sea to Atlantic Europe, Scandinavia, and the western Mediterranean, but new dating and analyses are needed to test this model.
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