## 3 Results and Discussion
### Raman Spectroscopy  
For an in-depth study of mosaic samples regarding vibration spectra, Raman spectroscopy was performed. Several characteristic Raman spectra are shown in Figures 4 and 5. The intensity Raman lines at 352, 462 and 1375 cm\({}^{-1}\) can be attributed to the phase of \(\alpha\)-quartz [44], while the most intense mode at 1087 cm\({}^{-1}\) corresponds to calcite [45]. Several weak peaks at 300 and 406 cm\({}^{-1}\) were assigned to hematite (Figure 5). The weak Raman peaks at 1305 and 1597 cm\({}^{-1}\) could be attributed either to amorphous carbon, hematite or \(\alpha\)-quartz phases [44; 45; 46].  
The results of a more detailed scan of the surfaces of mosaic samples 5 and 6 are shown in Figure 5. Raman spectra were obtained from various local areas of mosaics fragments characterized by a red or black color.  
Figure 4: Raman spectra obtained from surfaces of samples 1 and 2 and corresponding to calcite and quartz phases. The tentative assignment of Raman lines is present in Table 4.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Element 1**} & **Sample 1** & **Sample 2** & **Sample 3** & **Sample 4** & **Sample 5** & **Sample 6** \\  & **(White)** & **(Red-Dark)** & **(Blue)** & **(Grey)** & **(Red-Light)** & **(Black)** \\ \hline C & 5.64 \(\pm\) 0.06 & 9.26 \(\pm\) 0.06 & 7.15 \(\pm\) 0.05 & 8.07 \(\pm\) 0.07 & 12.57 \(\pm\) 0.08 & 8.15 \(\pm\) 0.08 \\ O & 39.06 \(\pm\) 0.24 & 52.22 \(\pm\) 0.29 & 43.44 \(\pm\) 0.24 & 47.66 \(\pm\) 0.26 & 45.56 \(\pm\) 0.29 & 45.09 \(\pm\) 0.26 \\ F & nd 2 & \textless{LOD }3 & nd 2 & \textless{LOD }3 & 0.79 \(\pm\) 0.14 & \textless{Lod }3 \\ Na & 0.15 \(\pm\) 0.02 & nd 2 & nd 2 & 0.43 \(\pm\) 0.02 & nd 2 & 0.42 \(\pm\) 0.02 \\ Mg & 0.36 \(\pm\) 0.02 & 0.41 \(\pm\) 0.03 & 0.53 \(\pm\) 0.02 & 8.25 \(\pm\) 0.05 & 0.63 \(\pm\) 0.03 & 0.93 \(\pm\) 0.02 \\ Al & 0.39 \(\pm\) 0.02 & 0.83 \(\pm\) 0.03 & 0.71 \(\pm\) 0.03 & 0.58 \(\pm\) 0.03 & 1.07 \(\pm\) 0.04 & 1.92 \(\pm\) 0.04 \\ Si & 0.38 \(\pm\) 0.03 & 1.44 \(\pm\) 0.03 & 1.14 \(\pm\) 0.03 & 1.20 \(\pm\) 0.04 & 2.67 \(\pm\) 0.04 & 4.99 \(\pm\) 0.05 \\ p & nd 2 & nd 2 & nd 2 & 0.42 \(\pm\) 0.04 & nd 2 & nd 2 \\ S & nd 2 & 1.24 \(\pm\) 0.02 & 0.18 \(\pm\) 0.03 & 1.25 \(\pm\) 0.02 & 0.65 \(\pm\) 0.04 & nd 2 \\ Cl & 0.21 \(\pm\) 0.02 & nd 2 & nd 2 & nd 2 & 0.52 \(\pm\) 0.03 \\ K & 0.23 \(\pm\) 0.03 & 1.28 \(\pm\) 0.07 & 0.34 \(\pm\) 0.06 & 0.95 \(\pm\) 0.03 & 0.48 \(\pm\) 0.07 & 0.92 \(\pm\) 0.08 \\ Ca & 53.56 \(\pm\) 0.27 & 33.32 \(\pm\) 0.20 & 46.50 \(\pm\) 0.23 & 31.20 \(\pm\) 0.20 & 35.59 \(\pm\) 0.22 & 37.06 \(\pm\) 0.22 \\ \hline \hline \end{tabular}  
* The detection and quantification were done with K-lines, for all elements; 2 nd—element which was not detected in sample; 3 element which was detected in sample; 3 element which was detected in sample and appear in EDS pattern (Figure 2c,g,k), but the concentration is less than the limit of detection (LOD \(\approx\) 0.01 wt.%).  
\end{table}
Table 3: The major and minor elements determined by FE-SEM-EDS in the studied mosaics fragments, expressed in wt.% \(\pm\) S.D.%, normalized to 100 wt.%.  
The tentative assignments of the visible Raman lines are presented in Table 4. In addition to the phases already described above, the Raman lines associated with hydroxides and oxides of iron and manganese were observed on Raman spectra of red crystallites on the surface of mosaic sample 5. The Raman peaks in the wavenumber region of 860-940 cm\({}^{-1}\) are related to the presence of some orthosilicates in the studied samples.  
The combination of these additional phases probably indicates the presence of a mixture of natural pigments; \"yellow ochre\" and \"red ochre\" were used as paint for mosaic glasses [14; 15; 46]. The black layer of sample 6 is characterized by two additional peaks at 1325 and 1610 cm\({}^{-1}\) (Figures 4 and 5 and Table 4). They are associated with a pure carbon phase [14]. It can indicate the presence of \"soots\" that were used as colorant for black mosaic sample [47].