Gava Neolithic Mines Archaeological Park, Barcelona, Catalonia, Spain. This is the site of a prehistoric variscite mine, a semi-precious green mineral which was used to make jewellery and was traded across the Western Mediterranean. These mines were exploited between 4200 and 3400 BCE (Neolithic period), making them the oldest known gallery mines in Europe and the only ones extracting variscite. Once all of the variscite had been extracted, parts of the mines were repurposed for human burial.