## 3 Results
### Carbonate Pigments
\\ \cline{2-5}  & 770 & \(\beta\)(CO\({}_{3}\)\({}^{2-}\)), malachite [52] & 770 & CO\({}_{3}\)\({}^{2-}\), malachite (?) \\ \hline \multirow{7}{*}{MA-S} & 776, 745, 705 & \(\beta\)(CO\({}_{3}\)\({}^{2-}\)), malachite [52] & 680 & Si–O, quartz [35] \\ \cline{2-5}  & 3403, 3320 & \(\delta\)(–OH), malachite [18] & 3700–3000 & \(\
u\)(–OH), malachite [9] \\ \cline{2-5}  & & & 1850, 1594 & CO\({}_{3}\)\({}^{2-}\)[26], malachite (?) \\ \cline{2-5}  & 1490, 1382 & \(\
u_{\text{as}}\)(CO\({}_{3}\)\({}^{2-}\)), malachite [18; 52] & 1478 & CO\({}_{3}\)\({}^{2-}\), malachite (?) \\ \cline{2-5}  & 1105 & \(\
u_{\text{s}}\)(CO\({}_{3}\)\({}^{2-}\)), malachite [52] & 1129, 1090 & \(\
u_{\text{s}}\)(CO\({}_{3}\)\({}^{2-}\)), malachite [9] \\ \cline{2-5}  & 1047, 873 & \(\beta\)(-OH), malachite [52] & 940–910 & Si–O, quartz [25] \\ \cline{2-5}  & 815 & \(\delta\)(CO\({}_{3}\)\({}^{2-}\)), malachite [52] & 845 & \(\delta\)(CO\({}_{3}\)\({}^{2-}\)), malachite (?) \\ \cline{2-5}  & 750,712 & \(\beta\)(CO\({}_{3}\)\({}^{2-}\)), malachite [52] & 769, 695, 675 & Si–O, quartz [26] \\ \hline \multirow{7}{*}{WL-S} & 3560–3100 & –OH [26], hydrocerussite (?) & 3800–3200 & \(\
u\)(–OH), hydrocerussite [14; 70] \\ \cline{2-5}  & 1730, 1065 & \(\
u_{\text{s}}\)(CO\({}_{3}\)\({}^{2-}\)), cernussite [14; 71] & 1780, 1135, 1080, 1020 & \(\
u_{\text{s}}\)(CO\({}_{3}\)\({}^Regarding copper carbonates, azurite is a basic blue copper carbonate (Cu\({}_{3}\)(CO\({}_{3}\))\({}_{2}\)(OH)\({}_{2}\)). The natural version (AZ-N) was additionally composed of quartz, kaolinite and phlogopite by XRD, all of which are common impurities to which the mineral ore is associated [74]. As for AZ-S, calcite was also present, related to the raw materials used in its manufacturing process [74]. When comparing AZ-N and AZ-S (Figure 8), differences between them were observed. The presence of impurities in the natural pigment, recognizable through the characteristic bands of kaolinite (-OH and Al-OH bonds [35; 42]) and those assigned to quartz (Si-O bonds [8; 34; 35]), in both ATR-FTIR and DRIFT spectra, marked a clear distinction between both pigments. Even though these bands were also present in both modalities, though present at higher wavenumbers in DRIFT spectra, other IR bands were observed. Both AZ-N (Figure 8b) and AZ-S (Figure 8d) showed bands assigned to organic matter (OM) which could be related to a levigation process. This is very remarkable since DRIFT modality was able to obtain IR signals (of considerable intensity) assigned to organic matter when ATR-FTIR spectra were unable to provide significant signals. Figure 8: Absorbance spectra of natural azurite (AZ-N) obtained by ATR-FTIR (**a**) and DRIFT (**b**) modalities and synthetic azurite (AZ-S) by ATR-FTIR (**c**) and DRIFT (**d**) modalities. See Table 1 for the explanation of the pigment identification codes. Malachite is also a copper carbonate (Cu\({}_{2}\)(CO\({}_{3}\))(OH)\({}_{2}\)), similar to azurite, therefore sharing similar absorption bands regarding hydroxyl (-OH) and carbonate (CO\({}_{3}\)\({}^{2-}\)) groups, as observed in Table 4. Natural malachite (MA-N) was also composed of hematite and cuprite, impurities to which the mineral ore is commonly associated [49]. However, none have IR signals in the 4000-650 cm\({}^{-1}\) spectral region. As for synthetic malachite (MA-S), quartz was also present related to the raw materials used in the pigment manufacture [49]. The ATR-FTIR spectra of both MA-N (Figure 9a) and MA-S (Figure 9c) presented very similar -OH and CO\({}_{3}\)\({}^{2-}\) group characteristic bands, though at slightly higher wavenumbers (\(\pm\)5 cm\({}^{-1}\)) in MA-S. As for the DRIFT spectra, results were very similar between them. Figure 9: Absorbance spectra of natural malachite (MA-N) obtained by ATR-FTIR (**a**) and DRIFT (**b**) modalities and synthetic malachite (MA-S) by ATR-FTIR (**c**) and DRIFT (**d**) modalities. See Table 1 for the explanation of the pigment identification codes.