Mining wastes are often both a potential source of Strategic and Critical Raw Materials (SRMs and CRMs) and a threat to the environment. This study investigated the potential of mining wastes from the Montevecchio district of Sardinia, Italy, as a source of SRMs and CRMs. The tailings from Sanna mine processing plant were characterized by X-ray diffraction, Scanning Electron Microscopy, and Plasma Mass Spectometry, showing contents of 1.2 wt% of lead, 2.6 wt% of zinc, and about 600 mg/kg of Rare Earth Elements (REEs). White patinas formed in the riverbed, composed by Zn-bearing minerals (hydrozincite and zincite), also contain about 2900 mg/kg of REEs. Characterization of white patinas along the Rio Roia Cani evidenced that their precipitation from water also involves an uptake of Rare Earth Elements, enhancing their contents by an order of magnitude compared with tailings. The process of REEs concentration in Zn-bearing minerals of white patinas is a candidate as a tool for the economic recovery of these elements. These findings suggest that mining wastes from the Montevecchio district could be considered a potential resource for extracting SRMs and CRMs.

Italy is estimated to host thousands of abandoned mines, many of which contain large volumes of mine residues that negatively affect land and aquatic ecosystems, also posing a risk to human health. This study evaluates the effectiveness of spaceborne imaging spectroscopy combined with laboratory spectroscopy for characterizing the mineralogy and geochemistry of residues from the abandoned Montevecchio sulfide mine in southwestern Sardinia, a site recognized as a significant source of environmental pollution. Mine tailings and their downstream dispersion along the Rio Irvi River were systematically studied and sampled in the field. Collected samples were analyzed in the lab using an Analytical Spectral Device (ASD) spectroradiometer, complemented by powder X-ray Diffraction (XRD) for mineralogical characterization. Affected zones were subsequently mapped using the Environmental Mapping and Analysis Program (EnMAP) hyperspectral satellite data at a 30 m spatial resolution, by applying a polynomial fitting technique to the image spectra. The results reveal the presence of Fe- and Zn-bearing sulfates and oxy/hydroxides, indicative of acidic-to-circum-neutral drainage conditions in the mine tailings and along affected streams. Specifically, EnMAP was able to detect jarosite and subtle chemical and physical variations in Fe-hydroxides. This integrated approach enabled the delineation of environmental conditions and zones with varying acidity based on the spectral characteristics of secondary minerals. Overall, the study demonstrates the potential of EnMAP data for mapping acid mine drainage and assessing environmental impacts in legacy mining areas.

Modern society bases its economic and industrial development on the use of advanced technologies, which are produced using materials and metals defined in the European Union as critical and strategic raw materials about the risk of their supply, linked to geological and geopolitical factors, and their relevance for the European chain of value. The CRM Act approved by the European Parliament addresses the future policies on CRM and SRM of the Member States, particularly for the development of primary (mining) and secondary (recycling) sources of these materials. In the context of recycling policies, particular emphasis is given to the necessary evaluation of the potential of waste from past extractive activities. As a part of the wider Project Geoscience IR coordinated by the Italian Institute for Environmental Protection and Research (ISPRA), the University of Cagliari (UniCa) is carrying out a study on Sardinian mining dumps, which provides for their mapping and characterization through sampling and laboratory activities, to investigate their possible content in CRMs. The first studies focused on SW Sardinia districts, have produced encouraging results, with the identification of the presence of CRMs in different types of wastes of various localities. The first target area is that of Montevecchio, once one of the largest mine districts in Italy, which now hosts over 13 million cubic meters of mining and processing wastes from the exploitation of a large Pb-Zn hydrothermal vein field. The study highlighted the economic potential of some of these materials, rich in Zinc (2.6%), Lead (1%) and Rare Earth Elements (about 600 ppm). In the south of Montevecchio, a second area of inferred high potential is the Fluminese region, marked by several kinds of CRM-bearing hydrothermal ore deposits. In this area, the mine dumps of the old Santa Lucia fluorite-barite mine are currently under study. Apart from fluorite and barite, they are suspected to host Ni-Co minerals and some amount of REE, given the wide chromatic variety of fluorites and the presence of Agardite-Ce in the mineralization. A third target under study is the Sulcis district, a historical mining area with numerous mine dumps scattered over a wide territory. Among them, of particular interest are the wastes related to the exploitation of Fe (magnetite) and Pb-Zn-Cu sulfide skarn ores, often marked by W and Sn contents. The goal of the Project is to produce a database containing information on CRMs contents in the various Sardinian historical mining dumps, and a new metallogenic map of Sardinia that may include the waste deposits of possible economic interest, which were not reported in the two previous produced editions. The map will constitute a model for broader mapping of Italian resources at a national scale. Keywords: Sardinia, mining dumps, critical and strategic raw materials, environmental sustainability

The sustainable management of mining wastes, a byproduct of extractive activities, represents a critical challenge in the context of the Critical Raw Materials Act (European Commission, 2023) and the transition to a circular economy. Mining waste dumps may contain significant residual amounts of ore minerals or metals, including Critical Raw Materials (CRMs), making their mapping and evaluation essential for environmental remediation and possible resource recovery. Developing detailed regional or national maps is pivotal to identifying mining waste dumps' location, typology, distribution, and spatial extent. Integrating Geographic Information System (GIS) software with complementary tools such as Google Earth, topographic maps, and orthophotos offers a comprehensive approach to efficiently identifying and analysing these sites.Sampling and characterising mining waste dumps is crucial to assessing their economic potential and environmental impact (Beltré et al., 2023). Mineralogical analyses (e.g., X-ray diffraction, Scanning Electron Microscopy, RAMAN, and Electron Microprobe) and chemical analyses (e.g., Portable X-ray Fluorescence, ICP-MS, or ICP-OES) enable the evaluation of mineral processing residues. This differentiation helps identify economically viable dumps and prioritise remediation efforts for non-viable sites with contamination risks. (Lemière et al., 2011)These methodologies are now applied to developing the Metallogenic Map of Sardinia, which will include the mapping of different mining waste dumps in Sardinia and their sampling.The crucial challenges of this project are accurately estimating dump volumes due to difficulties in identifying underlying bedrock and quantifying critical metal content. Addressing these gaps is crucial for effective resource valorisation and site rehabilitation. To date, 140 mining waste samples have been collected and are under analysis to assess their economic and environmental potential. This study integrates GIS technologies with environmental and economic assessments as a pathway to support sustainable exploitation and management of mining waste dumps, aligning with EU strategic goals for CRMs. Keywords: Critical Raw Materials, Circular Economy, Resource valorisationEuropean Commission (2023) - Study on the Critical Raw Materials for the EU. Fifth list. Final report. Rosario-Beltré, A. J., Sánchez-España, J., Rodríguez-Gómez, V., Fernández-Naranjo, F. J., Bellido-Martín, E., Adánez-Sanjuán, P., & Arranz-González, J. C. (2023). Critical Raw Materials recovery potential from Spanish mine wastes: A national-scale preliminary assessment. Journal of Cleaner Production, 407. https://doi.org/10.1016/j.jclepro.2023.137163 Lemière,, Cottard, F., & Piantone BRGM, P. (2011). Mining waste characterization in the perspective of the European mining waste directive.