They demonstrate how the Romans exploited gold mines in the Pyrenees

BarcelonaThe Pyrenees are not 19th-century California, when thousands of people from all over the world flocked there in search of fortune, nor are they South Africa. Even so, there were also gold mines there that the Romans exploited. This has been demonstrated, for the first time, by a study from the Autonomous University of Barcelona (UAB) and the University of A Coruña. "We know that the Guilleteras mines in All (Cerdanya) were exploited between the 1st and 3rd centuries AD. We have indications that there must have been more mines in the Pyrenees, but that they must have been abandoned when they found more profitable ones elsewhere, such as Las Médulas (León), or in northern Portugal," the study explains.

The researchers' first clue appeared in a Roman necropolis located near All (Isòvol), in the Pla de Prats, less than a kilometer from the mines. There they found a 27-gram gold chain. In Castellot de Bolvir, a second clue was found: a 1st-century BC metallurgical workshop with traces of gold and silver particles. To demonstrate that the mines were exploited in All, a large hydraulic reservoir that formed part of the mining system was excavated. The problem was being able to date it, because there are practically no archaeological materials. "In 2022, an OSL dating strategy was initiated (optically stimulated luminescenceThis technique allows us to date detrital sedimentary materials, especially quartz, because when buried in an archaeological layer, they begin to receive a flow of radioactive particles that we can measure and date. This dating is not as precise as C14, but it has the advantage of not requiring organic matter,” explains Olesti.

The technique for extracting gold

It was known that there was gold in the terraces of the Segre River. In fact, Islamic sources already spoke admiringly of its high quality for minting coins. However, until now there was no proof. "We shouldn't imagine a large-scale mining operation or slaves chipping away at the stone," Olesti explains. Nor should we imagine large quantities of gold, because from much more heavily mined areas, such as Las Médulas, only 250 tons were extracted over the centuries. The Romans used a hydraulic system to extract tiny gold nuggets from the granite rock. They built canals that stretched for dozens of kilometers, carrying water that was stored in reservoirs near the mining faces. These reservoirs were periodically emptied, and the water carried away the gold-bearing sediments, which settled further downstream. "It was more a matter of mastering the technique. Most likely, they used local people guided by an expert, possibly a military officer," Olesti asserts. One of these water channels, which connects All with Meranges and is fed by the Duran River, still exists. The mine was likely abandoned around the same time as the decline of Iulia Líbica (Llívia), about ten kilometers from the mines. Llívia was an important municipality in Roman Cerdanya, probably a control and trading point between valleys, and was home to both newly arrived people from Italy and those displaced from the region's settlements.