## 3 Results and Discussion  
Considering the \"asbestos\" minerals, more or less numerous particles, mostly rounded and micrometric in size, were observed on their fiber surface under OM, Figure 2. The phenomenon was particularly evident on amosite, Figure 2a, where the fibers were practically recovered both by fine fibrils and by small particles. Also crocidolite, Figure 2b, and chrysotile, Figure 2f, exhibited many dark particles on their surface, but also areas free from these foreign phases could be observed. On tremolite, anthophyllite and actinolite, the presence of round grains was less frequently noticed, Figure 2c-e.  
Figure 2: Optical Microscopy images of the six regulated asbestos minerals: (**a**) amosite; (**b**) crocidolite; (**c**) tremolite; (**d**) anthophyllite; (**e**) actinolite; (**f**) chrysotile. The data from micro-Raman spectroscopy can be analyzed for the spectral region where lie the vibrational modes ascribed to the three-dimensional lattice of the mineral phases, 1200-100 cm\({}^{-1}\), and for the spectral range, 4000-1200 cm\({}^{-1}\), where lie the non-reticular vibrational modes. As it concerns the first spectral region, the results are shown in Figure 3. The Raman spectra appeared very rich in bands, especially in amphiboles, as a consequence of the different chemical bonds in the crystal structure (Si-O\({}_{\text{b}}\)-Si, Si-O, bonds between various cations and tetrahedral oxygens or OH\({}^{-}\) groups... ), therefore the attribution of each band to a single vibrational mode is very hard and in any case beyond the aim of this work. A discussion about the vibrational modes produced by the stretching modes, both symmetric (\(\
u_{\text{s}}\)) and antisymmetric (\(\
u_{\text{as}}\)), of the different Si-O linkages has been proposed in [PERSON] et al. 2004 [26], and recently determination of the chemical formulae of various amphiboles by Raman spectroscopy has been suggested by [PERSON] et al. 2019 [29]. On the contrary, the Raman spectrum from chrysotile appeared poorer in bands, consequence of a crystal structure formed by only two types of polyhedra--SiO\({}_{4}\) and Mg(O, OH)\({}_{6}\). For the serpentine minerals, an attribution of the detected Raman bands to the different vibrational modes has been described in [PERSON] et al. 2003 [30]. Being interested in the identification of the mineral phase, it can be achieved considering the region where lie the symmetric stretching modes (\(\
u_{\text{s}}\)), 700-600 cm\({}^{-1}\), and antisymmetric stretching modes (\(\
u_{\text{as}}\)), 1100-1000 cm\({}^{-1}\), of the Si-O\({}_{\text{b}}\)-Si linkages, Figure 3. In fact, the difference in wavenumbers where lie the \(\
u_{\text{s}}\) modes is higher than the instrumental error, 2 cm\({}^{-1}\). A particular situation involves tremolite and anthophyllite, where the \(\
u_{\text{s}}\) modes vibrate very close. In this case, considering also the wavenumbers of the \(\
u_{\text{as}}\) stretching modes (1044 cm\({}^{-1}\) in anthophyllite and 1062 and 1031 cm\({}^{-1}\) in tremolite), a sure identification can be achieved. As it concerns chrysotile, the \(\
u_{\text{s}}\) modes vibrate at higher wavenumber, about 694 cm\({}^{-1}\), with respect to all the amphibole asbestos phases. Concerning the \(\
u_{\text{as}}\) stretching modes, lying at 1105 cm\({}^{-1}\), it is often undetectable for the presence of intense bands  
Figure 3: Spectra obtained on the six regulated asbestos minerals in the spectral range 1200–100 cm\({}^{-1}\): (**a**) amosite; (**b**) crocidolite; (**c**) tremolite; (**d**) anthophyllite; (**e**) actinolite; (**f**) chrysotile. Considering the \(\
u_{\text{s}}\) and \(\
u_{\text{as}}\) modes of the Si-O\({}_{\text{b}}\)-Si bonds, a sure identification of the mineral phase can be obtained. produced by carbonaceous materials (CMs) lying on the crystal surface [31], Figure 3f, as will be after discussed.