Mining and geological knowledge during the Neolithic: a geological study on the variscite mines at Gavà, Catalonia

The Gava Neolithic Mining Complex (GNMC) near Barcelona was active during the Neolithic age, since ca. 6000 BP until about 700 years after. These mines show up to five different underground mining levels, developed as galleries and chambers, communicated through pits, drawing a complex network with a total known length of over 1000 m. These are some of the oldest underground mines in Europe but, contrary to the rest of the mine workings known of the same epoch, this is the only mining complex reported to date whose aim was not mining for conventional substances for the epoch such as chert, ochre or copper. The main aim of the GNMC was variscite, a green phosphate mineral similar to turquoise that can be easily cut and polished to make ornaments such as necklaces or bracelets. This paper is focused mainly on the geological mapping and examination in surface and underground exposures of the different phosphate mineralization types (stratabound and veins) and other relevant geological features such as discordances, thrusts, faults, and folds.