Mine waste as a dual threat and opportunity: Linking mineralogy to environmental impact and critical element recovery

Abandoned mine waste is both a significant environmental liability and a potential secondary source of critical raw materials (CRMs). This study provides an integrated geochemical and mineralogical assessment of two contrasting waste deposits from the Trimpancho mining complex (Iberian Pyrite Belt, SW Europe). Bulk chemical analyses, XRD and TEM/SEM-EDX mineralogy, and sequential extraction were combined with UAV-derived volumetric estimates to evaluate contaminant mobility and CRM recovery potential. The sulfide-rich Nuestra Señora del Carmen (NSC) dump, integrating the Trimpancho mining complex, is dominated by Fe and S, with marked chemical heterogeneity and high concentrations of As, Cu, Pb, and Zn. Mineralogical analyses revealed abundant sulfide alteration products (jarosite and goethite) and clay minerals, which influence potential contaminant retention and mobilization. Sequential extraction results showed high potential mobility for Mn, Zn, Cu, and, locally, As and Pb, translating into mobilizable loads in the order of 10⁴ t. In contrast, the Volta Falsa (VF) dump, composed mainly of roasted pyrite slag and Fe oxides, displayed lower S contents, greater homogeneity, and negligible mobilizable contaminant loads, consistent with its more stable mineral assemblage. From a resource perspective, only NSC exhibits significant CRM potential, primarily for Cu (∼175-246 t), with minor contributions from Co, Sb, and LREEs. VF, despite locally elevated Cu concentrations, is constrained by its limited volume. These findings highlight the dual significance of mine waste as both environmental hazards and potential secondary mineral resources. Integrated strategies that couple risk mitigation with selective CRM recovery represent a promising pathway for sustainable management of mining legacies and align with international efforts toward circular resource use.