First update of the regional database of storage facilities (mining and mining-metallurgical waste deposits) in Sardinia

This doctoral thesis presents the first regional-scale inventory and geospatial database of mining and metallurgical waste deposits in Sardinia (Italy), developed within an ISPRA–UniCa project funded by the Italian PNRR. The study addresses the growing interest in mining waste as a potential secondary source of Critical Raw Materials (CRMs), aligning with the European Critical Raw Materials Act and circular economy principles. Sardinia, a historically significant mining region in the Mediterranean (Pb, Zn, Ag, Cu, Sb, W, etc.), has a large number of waste deposits from past activities. However, information on these 1,887 sites was historically fragmented across technical reports, archives, and non-standardized surveys. To fill this gap, a unified geodatabase was created by integrating bibliographic research, archival data, historical mining maps, and GIS-based spatial analysis. Each site was georeferenced and classified by typology, geological setting, mining district, surface extent, and potential CRM-bearing mineral phases. Key findings from statistical analysis show: - A skewed distribution: a limited number of large deposits dominate the regional mining-waste footprint. - Spatial distribution closely reflects the main metallogenic districts and historical mining organization. - A clear relationship exists between waste typology, processing history, and qualitative CRM occurrence. The thesis comprises three scientific contributions: 1. A critical review of the origin, typology, environmental impacts, and resource potential of Sardinian mining wastes. 2. A mineralogical and geochemical study of the Montevecchio district, focusing on Zn and REE enrichment in tailings and secondary biomineralizations. 3. A multi-analytical characterization of the Fluminése–Arburése district, documenting REE-bearing minerals (synchysite-(Ce)), fluorite, baryte, and elevated Bi and Sb concentrations. The research concludes that Sardinia's mining waste deposits are not only an environmental liability but also a potentially valuable secondary resource. The presence of CRMs (REEs, Bi, Sb, Ba, F) and residual base metals supports integrated valorization and remediation strategies aligned with the European Green Deal. The resulting geodatabase is a fundamental tool for environmental monitoring, territorial planning, and secondary resource assessment. The methodological approach is replicable and can be applied to other Italian and European regions with similar mining legacies.