The S. Domingos abandoned mine is a major source of pollutant-metals contamination. Slags from the 19th–20th century contain the most hazardous material. However, the release of pollutant metals depends on the metal-retention capability of weathering products. This work shows that Zn is not effectively retained by these weathering products while As and Pb are partially stored in sulphates. Copper, on the other hand, has a different behaviour and is the most leachable of the elements studied.