Unveiling High-Tech Metals in Roasted Pyrite Wastes from the Iberian Pyrite Belt, SW Spain

The Iberian Pyrite Belt (IPB), in the southwestern Iberian Peninsula, is a large metallogenic province exploited since ancient times. As a result of historical and current mining activity, a vast volume of metallic mineral waste, mainly derived from the processing of pyrite, is still in situ and polluting the environment. A specific mine waste residuum locally known in the area as morrongos, which was produced during pyrite roasting mainly in the 19th century, is evaluated here in order to unravel untapped resources of high-tech metals commonly used in high-tech devices. Applying a combination of whole-rock geochemical (ICP-AES, ICPMS, FA-AAS) and single-grain mineralogical techniques (EPMA, LA-ICP-MS, FESEM, and FIB-HRTEM) on the morrongos, we unhide the still-present remarkable concentrations of Au, Ag, Pb, Zn, and Cu in them. The mineralogical expressions for these economic metals include oxides (hematite, magnetite, and hercynite), arsenates, sulfates of the jarosite group, native metals, and, to a lesser extent, relictic sulfides. This first-ever estimation of these economic metals in this type of residue allows their revalorization, highlighting them as suitable sources for the exploitation and recovery of metals necessary for the clean energy transition.

Automated summary

This article evaluates a type of mine waste residue called morrongos in the southwestern Iberian Peninsula, and discovers significant concentrations of high-tech metals in them. By using both whole-rock geochemical and single-grain mineralogical techniques, remarkable concentrations of gold, silver, lead, zinc, and copper are uncovered. This first-ever estimation of these economic metals in this type of residue provides important metal resources for the clean energy transition.