A cave in the Pyrenees reveals the secret of how copper was made 5,000 years ago

BarcelonaAt about 2,250 meters above sea level, in the Natural Park of the Headwaters of the Ter and Freser, halfway between the monastery of Núria and the summit of Puigmal, there is a cave that was occupied intensively, and not sporadically, between the fifth millennium BC and the end of the first millennium BC. Named Cova 338, it is the most important high-mountain prehistoric site documented in the Pyrenees mountain range. The latest discovery includes numerous combustion structures, faunal remains, ceramic fragments, and a notable collection of green minerals, probably malachite, which demonstrate that copper-rich minerals were systematically exploited there during the late Neolithic and the Bronze Age. This data places Cova 338 among the oldest known evidence of this type of activity in Western Europe.

It is not easy to access this cave. "The fence to protect it, we had to lower it with a helicopter," explains Carlos Tornero, a professor in the Department of Prehistory at the Autonomous University of Barcelona (UAB), who has led the research together with researchers from IPHES-CERCA, the Rovira i Virgili University (URV), the University of Granada, Pompeu Fabra University (UPF), and the University of the Balearic Islands (UIB), among other institutions. The study, which has been published in the scientific journal Frontiers in Environmental Archaeology, questions the traditional idea that these areas were only used sporadically or marginally. The dating indicates that occupations occurred in several distinct phases, separated by periods of abandonment, which points to a planned and recurrent use of the space. Until now, evidence of copper smelting at such an early age had never been found. "There were even studies that claimed that copper tools and objects had arrived from France, where sites have been found in the Gulf of Lion," explains Tornero.

A chemical revolution

Currently, the transformation of malachite into copper may seem like a relatively simple chemical process, but in prehistory, it represented a true technological revolution. It is not known how they discovered how to make copper, but it was a long and physically exhausting process. Caves were not just shelters; they were the first laboratories where they attempted to master the invisible, oxygen. To extract copper, those early metallurgists did not need large structures. The key was in the ground. They dug small pits where they mixed the fuel – charcoal – with the previously crushed malachite.Within these rudimentary structures, and often with the help of blowpipes to feed the flames, the heart of the fire reached temperatures of up to 1,000 degrees. It was only a first step, because one could have a blazing fire and not obtain a single drop of copper. The true technological complexity of prehistory lay in gas management. It was necessary to create a very oxygen-poor environment; to do this, large quantities of charcoal were added and, upon losing its oxygen, the malachite decomposed and pure copper emerged in the form of small bright droplets among the embers.Among the materials recovered from the cave, two pendants also stand out, one made from a seashell (A pendant with a bone tooth

Among the materials recovered in the cave, there are also two pendants, one made from a marine shell (Glycymeris) and another with a brown bear tooth, which were surely personal ornaments. It is not exceptional to find pendants made from shells, but it is not at all common to find those made from bear teeth and it possibly had some symbolic meaning.

About five thousand years ago the area was full of forests, which gradually disappeared with livestock farming. "It was an alpine landscape, with a climate similar to ours; in winter there is a lot of snow, which is why it required planning, because one could only go there for a few months a year, and it makes sense that the exploitation was in this cave because nearby there is a malachite collection point," explains Tornero. The recovered evidence indicates that the mineral fragments were introduced into the cave and subsequently fragmented or processed inside, which suggests a systematic exploitation of copper-rich minerals. At the site, researchers have found evidence of a clear internal organization of activities, with differentiated structures and areas. “This site shows that the Pyrenees were not a marginal territory for prehistoric communities, but a space fully integrated within their mobility and territory exploitation strategies,” concludes Tornero.