## 1 Introduction  
The reliable and unimpeded access to certain raw materials is a growing concern worldwide, particularly within the European Union (EU). The EU, in the coming years, will require substantial quantities of raw materials to achieve the objectives set by the European Green Deal regarding ecological and digital transition to address climate change [1]. For these reasons, as early as 2011, the European Commission defined a list of raw materials labelled as \"Critical\" (CRM) essential for the European economy. These materials form a solid industrial base, producing a wide range of goods and applications used in daily life and modern technologies. This list has been periodically reviewed and updated based on its importance to the EU economy and the risk of supply [2, 3, 4, 5, 6]. The EU's concerns on these matters culminated with UE 2024/1252 \"Critical Raw Materials Act\" aimed at creating secure and resilient supply chains, mitigating supply risks, improving sustainability and circularity of critical raw materials in the EU market, and diversifying EU raw material imports [6, 7]. The CRMs Act introduced clear deadlines for the authorization procedures of extraction projects within the EU and required member states to develop national exploration plans to ensure the EU's access to critical and strategic resources. Additionally, three key benchmarks for the consumption of critical raw materials in the EU were established: at least 10% of the materials used must be extracted within the EU; at least 40% of the raw materials used must be processed within the EU; and at least 25% of the raw materials used must come from recycling [7]. Since 2023, feldspars have been included in the list of CRMs due to the escalating supply risk, notably stemming from heightened dependence on imports and the doubling of imports from Turkey, which now accounts for 51% of the EU's demand [6; 8]. Feldspars are used widely in the glass and ceramics industries, and they are recovered from different geological sources: 37%--albitties, 24%--pegmatites and aplites, 16%--granitoids, 11%--feldspathic arenites, 6.5%--nepheline sevites, 2.5%--rhyolites and porphyrins, and 3%--metamorphic and epithermal alterations [9]. In this context, the exploration of raw material sources from unconventional deposits could be of remarkable importance, as it would help diversify supply sources. For instance, ornamental granite extraction waste could be a favorable source of raw materials for the glass and ceramics industries [9]. In Italy, the region of Sardinia boasts a long-standing tradition in the extraction of granitoid rocks for ornamental purposes. Sardinia reached a leading position as a manufacturer of granite in Italy, increasing from 1.5% of Italian production of granite in 1961 to 50% in 1971. It reached its peak production in the 1990s, becoming the leading producer of granite in Italy, representing 90% of the national production [10]. However, the significant success of the granite extraction industry began to decline from the mid-2000s, primarily due to the entry of other international competitors into the global market, as well as significant infrastructural challenges on the island of Sardinia [10]. The production of granite in Sardinia has decreased from just over 1.0 Mg in 2001 to just under 0.2 Mg in 2012 [10]. Moreover, it is likely that the financial crisis of 2007-2008 and the COVID-19 pandemic have contributed to exacerbating the crisis in this sector. This has inevitably brought serious consequences for the economy of Sardinia, causing the closure of numerous companies and a significant loss of jobs. Just as granite extraction has had a significant positive impact on the economy of Sardinia and Italy during the best period of this sector, it has also had an equally strong negative impact on the Sardinia landscape, both due to the presence of quarries and the vast amount of waste materials derived from them.