The antimony (Sb) resource in southern Tuscany (Italy): A multi-scale approach from textural and geochemical characterization to 3D geological modeling (Montauto mining area)

Europe is highly dependent on foreign suppliers for several critical raw materials (CRMs), owing to limited domestic mining production. Antimony (Sb) has been included among Europe’s CRMs since the first list published in 2011, due to its extensive use in strategic industrial sectors. To meet the steadily increasing demand, new Sb orebodies must be identified, explored, and exploited within the European Union to diversify supply chains and reduce geopolitical risks. In parallel, the recovery of Sb from secondary sources, such as historical mining wastes, represents an additional opportunity.  

Within this framework, Italy has adopted the EU Critical Raw Materials Act, promoting the development of a national exploration plan. Antimony was historically mined in two Italian regions, Tuscany and Sardinia, leaving a substantial legacy of geological data (e.g., mining reports and drill logs) as well as significant volumes of mineral wastes. These Sb districts, where stibnite (Sb₂S₃) is the main economic mineral, represent an exceptional case study for assessing the potential Sb resources and associated CRMs in Italy. This study focuses on the Tuscan Sb district (e.g., the Mancianese area, southern Tuscany), where most of the available geological information is outdated and where robust constraints on orebody geometries, volumes, and associated CRM contents are still lacking (e.g., Lattanzi 1999). Here, we present the first results of an ongoing research project aimed at: 

• Geological, mineralogical and geochimical data of Sb resources in Tuscany unravel ore genesis ;   

• a 3D geological model of the selected orebodies, and potentially unexploited bodies, with probabilistic functions to conduct uncertainty analysis.  

Field surveys and sample collection were carried out in the Mancianese area and were integrated with textural analyses (reflected-light microscopy and SEM), mineral chemistry investigations (EPMA and LA-ICP-MS), stable and radiogenic isotope analyses and fluid inclusion studies. The collected dataset was used to reconstruct a 3D model of selected orebodies using GemPy, an open-source, Python-based geological modeling software. The results highlight the subsurface extent and continuity of mineralization, allowing a first-order estimate of the potentially available Sb resources. The resulting geological model not only contributes to the evaluation of the Italian Sb mining potential, which remains poorly constrained to date (SCRREEN, 2023), but also provides a robust framework for reconstructing the processes responsible for stibnite mineralization. This represents a valuable basis for future exploration and prospection campaigns in Southern Tuscany, offering essential knowledge for characterizing the mineral resource and developing genetic models that can also be applied to similar geological settings across Europe.