## 3 Results
### Sulphide Pigments
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Pigment**} & \multicolumn{2}{c}{**ATR-FTIR**} & \multicolumn{2}{c}{**DRIFT**} \\ \cline{2-5}  & **Wavenumber (cm\({}^{-1}\))** & **Assignment\({}^{1}\)** & **Wavenumber (cm\({}^{-1}\))** & **Assignment\({}^{1}\)** \\ \hline \multirow{6}{*}{CI-N} & \multicolumn{5}{c}{1686, 1556, 1490, 1434} & \multicolumn{2}{c}{CO\({}_{3}\)\({}^{-2}\), carbonate [26], calcite (?)} \\ \cline{2-5}  & 1248 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], cinnabar (?) & 1259 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], cinnabar (?) \\ \cline{2-5}  & 1135, 1033 & \(\
u\)(Si–O), quartz [8; 34] & 1075, 918, 897, 807, 700 & \(\
u\)(Si–O), quartz [35] \\ \cline{2-5}  & 875 & \(\
u_{\text{as}}\)(CO\({}_{3}\)\({}^{-2}\)), calcite [8; 45] & & \\ \cline{2-5}  & 743, 665 & \(\
u\)(Si–O), quartz [8; 34] & 667 & Si–O, quartz [35] \\ \hline \multirow{6}{*}{VE-S} & 3500–3000 & -OH [26] & 3846, 3700–3200 & -OH [26] \\ \cline{2-5}  & \(\sim\)1647, \(\sim\)1450 & \(\text{CO}_{3}\)\({}^{2-}\), carbonate [26], calcite (?) & 1698, 1591, 1495, 1434 & \(\text{CO}_{3}\)\({}^{2-}\), carbonate [26], calcite (?) \\ \cline{2-5}  & & & 1258 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], vermillion (?) \\ \cline{2-5}  & 1206 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], vermillion (?) & & \\ \cline{2-5}  & 1157, 1080, 1026, 661 & \(\
u\)(Si–O), quartz [8; 34] & 1099, 925, 803, 694, 677 & \(\
u\)(Si–O), quartz [35] \\ \cline{2-5}  & 875 & \(\
u_{\text{as}}\)(CO\({}_{3}\)\({}^{-2}\)), calcite [8; 45] & & \\ \hline \multirow{6}{*}{OR-N} & \(\sim\)1420 & \(\text{CO}_{3}\)\({}^{2-}\), carbonate [26], calcite (?) & 1690, 1491 & \(\text{CO}_{3}\)\({}^{2-}\), carbonate [26], calcite (?) \\ \cline{2-5}  & 1244 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], & 1285, 1260 & \(\
u_{\text{as}}\)(SO\({}_{2}\)) [26], \\ \cline{1-1} \cline{2-5}  & 1145, 1035, 845, 798, 710 & \(\
u\)(Si–O), quartz [8; 34] & 1180, 1140, 1070, 893, 860, 815, 700, 675, 660 & \(\
u\)(Si–O), quartz [35] \\ \cline{1-1} \cline{2-5}  & 870 & \(\
u_{\text{as}}\)(CO\({}_{3}\)\({}^{2-}\)), calcite [8; 45] & & \\ \hline \end{tabular} \({}^{1}\) Vibration mode: \(\
u_{\text{s}}\), symmetric stretching; \(\
u_{\text{as}}\), asymmetric stretching; \(\delta\), bending; (?), possible assignment.  
\end{table} 
Table 5: Sulphide-based pigments analysed by ATR-FTIR and DRIFT modalities. Bands (cm\({}^{-1}\)) and assignment (vibration mode and mineral associated) are included where possible. See Table 1 for the explanation of the pigment identification codes. Figure 11: Absorbance spectra of natural cinnabar (CI-N) obtained by ATR-FTIR (**a**) and DRIFT (**b**) modalities and synthetic cinnabar (CI-S) by ATR-FTIR (**c**) and DRIFT (**d**) modalities. See Table 1 for the explanation of the pigment identification codes. Overall, it was observed that the identification of sulphide pigments is not an easy task by IR spectroscopy, regardless of the modality. Though their impurities appeared in the spectra, the three pigments showed the same mineral phases (calcite and quartz). Therefore, the use of other portable techniques such as Raman spectroscopy should be considered for their identification. Nevertheless, it was observed that DRIFT modality provided more information than ATR-FTIR. Also, all three showed bands assigned to organic matter (OM) which could be related to a levigation process, where rabbit glue was used for CI-N and VE-S, and casein in OR-N, as explained in [27].