## 4 Discussion
### Raman Spectroscopy  
Raman spectroscopy is completely non-invasive and non-destructive, which are fundamental requirements to define it as a suitable chemical technique for cultural heritage analysis [68; 69]. It has been widely employed for the examination of different safeguarded objects like pottery, superficial deterioration coating of paintings and metal artefacts, glasses, inks, and human bones [35] whereas a small amount of research has been conducted on lithic archaeological findings [70; 71]. The present study interestingly combines qualitative and quantitative analysis of lithic artefacts to carry out the most complete and reliable mineralogical determination of bulk material. In fact, [PERSON] et al. (2015) [40] report an accuracy of 84% for matching entire spectra using CrystalSleuth functionality. In detail, the accuracy of the qualitative matching by CrystalSleuth strongly depends on peak quality and the spectral signal-to-noise ratio [72]. Despite its capacity to enhance the overall peak intensity, the 532 nm laser inevitably affects spectral quality due to its capacity to induce an increase in emitted fluorescence by minerals which is proportional to the fourth power of laser frequency [73]. For all these reasons, the quantitative methodology consolidates the qualitative results by determining the anorthite content (An(mol%)), which is extremely useful for the collocation of minerals into the plagioclase solid solution [61] and then for the discrimination between gabbro and diorite petrographic groups. Moreover, this approach gives the possibility to overcome the subjectivity of the common identification of raw material made through the naked eye observation [74]. In addition, the implementation of Raman spectroscopy results with QGIS technology establishes a methodology to pursue reliable provenance information for lithotypes, avoiding X-ray powder diffraction (XRPD) or SEM analysis, which require specimen treatment to obtain a detailed chemical analysis of trace elements [31; 71]. Nevertheless, the surface roughness and shape of MFP impede the accurate acquisition of some spectra and for this reason, its petrographic classification is less accurate than the others. Generally, surface irregularities, superficial patinas, and mineral orientation on the rocks usually change the quality of spectra acquisition and even cause the disappearance or shift of peaks [75]. In detail, the lithologies of R1, R2, R3, and R4 belong to the HP-metaophiolite category, a term that associates different lithologies deriving from the same metamorphic process that occurred on the oceanic crust and the underlying upper mantle during the abduction process [29]. HP-metaophiolite rocks are widely recognised as preferred stones for the lithitic industry of northern Italy, especially the so-called \"greenstone\" for polished stone tools like ring bracelets [22; 23; 24; 30]. However, during the first VBQ culture, there is evidence of an increase in the regional variability of the type of rock used to realise ornaments and other tools, and the widespread use of \"greenstone\" was gradually replaced by other lithologies because they are different from the usual greenstone lithotypes [23]. This trend seems to be confirmed by the results of the samples analysed in the present study. The QGIS examination of the geographical collocation of the lithological outcrops results in a significant overlap with the still-known primary sourcing area of the Monviso Massif and the Voltri Group along with the Beigua Unit [22; 23; 26; 27; 28; 31; 76]. Regarding the Voltri Group, R1, R3, and R5 may be derived from the Beigua Unit, consisting of metabasites associated with altered peridotite, whereas R2 and R4 may come from the Voltri Unit where serpentinites and calcschists are dominant [77]. The entire arc of the Western Alps may also be a primary supply area for the lithologies mentioned above, as well as for granulite which refers to the R5 sample.