## 2 Materials and Methods
Analyses were performed with Cu-K\(\alpha\) radiation, Ni filter, 45 kV voltage and 40 mA intensity. The exploration range was 3\({}^{\circ}\) to 60\({}^{\circ}\) 20 and the goniometer speed was 0.05\({}^{\circ}\) 20 s\({}^{-1}\). The oriented aggregate method was also used in green earth and natural ochre pigments since it is common for these pigments to have clay minerals in their composition. The mineral phases were identified using X'Pert HighScore software (version 4.9.0.27512). Table 1 compares the specifications provided by the supplier with those obtained from the mineralogical characterization conducted by the authors. The detection limit of this technique was ca. 3 wt.%; therefore, other mineral phases in low percentage could not be discarded. The molecular composition of the pigments was obtained by Fourier Transform Infrared Spectroscopy (FTIR) by directly analysing the powder pigments. The pigments were analysed using a laboratory FTIR benchtop Thermo Nicolet 6700 equipment (Thermo Fisher, Waltham MA, USA) with a 2 cm\({}^{-1}\) resolution in Attenuated Total Reflection (ATR) modality, with 100 scans (automatically averaged into a single spectrum), operating in the mid-infrared spectral region (4000-650 cm\({}^{-1}\)). The powdered pigments were individually analysed by placing less than 1 gram and pressing the plunger against a diamond crystal, exerting the maximum pressure that the equipment allows to ensure the best possible contact with the diamond crystal. A 4300 Handheld FTIR Spectrometer manufactured by Agilent Technologies S.L. (Santa-Clara, CA, USA) was also used in Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) modality, operating in the same infrared spectral region, with 32 scans (automatically averaged into a single spectrum), with a spectral resolution of 4 cm\({}^{-1}\) and a penetration depth of 2-3 \(\upmu\)m. A Coarse Gold Reference Cap (G8180-67560) was used for background subtraction. In this procedure, approximately 2-3 grams of each powdered pigment were individually placed on glass slides and then flattened by gently pressing another glass slide on top, creating a smooth and uniform \begin{table}
\begin{tabular}{c c c c c} \hline \hline \
\begin{tabular}{c} **Chemical** \\ **Nature** \\ \end{tabular} & **Suppliers Code** &
\begin{tabular}{c} **Authors** \\ **Code \({}^{*}\)** \\ \end{tabular} & **Supplier’s Composition** & **Authors’ Mineralogical Composition by XRD** \\ \hline \multirow{8}{*}{Carbonates} & \#10200 & & & Azurite, CuCO\({}_{3}\)Cu(OH)\({}_{2}\) \\  & Natural Azurite & AZ-N & Copper hydroxide carbonate & Quartz, SiO\({}_{2}\) \\  & & & & Kaolinite, Al\({}_{2}\)Si\({}_{2}\)O\({}_{3}\)(OH)\({}_{4}\) \\  & & & & Phlogopite, KMg\({}_{3}\)AlSi\({}_{0}\)O\({}_{10}\)(FOH)\({}_{2}\) \\ \cline{2-5}  & \#10180 & & & \\ Synthetic azurite & AZ-S & Basic copper carbonate & Azurite, CuCO\({}_{3}\)Cu(OH)\({}_{2}\) \\  & & & & Calice, CaCO\({}_{3}\) \\  & \#10300 & & & Malachite, CuCO\({}_{3}\)Cu(OH)\({}_{2}\) \\ Natural & NA-N & Copper hydroxide carbonate & Cuprite, Cu\({}_{2}\)O \\  & & & & Hematite, Fe\({}_{2}\)O\({}_{3}\) \\ \cline{2-5}  & \#4440 & & & \\ Synthetic & MA-S & Copper hydroxide carbonate & Malachite, CuCO\({}_{3}\)Cu(OH)\({}_{2}\) \\  & & & & Quartz, SiO\({}_{2}\) \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\  & & & & \\ \hline \multirow{8}{*}{Sulphides} & \#46000 & & & \\ White lead & WL-S & Lead carbonate, corussite & Cerussite, PbCO\({}_{3}\) \\ \cline{2-5}  & \#10624 & & & \\ Cinnabar & CI-N & Cinnabar & Cinnabar, HgS \\ \cline{2-5}  & \#42000 & & & \\ Vermilion & VE-S & Mercuric sulphide & Cinnabar, HgS \\ \cline{2-5}  & \#10700 & & & \\ \cline{1-1}  & \#10700 & & & \\ \cline{1-1}  & \#hyper & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline Acetate & \#44450 & & & \\ Verdigris & VER-S & Copper (II)-acetate-1-hydrate & Hoganite, Cu(CH\({}_{3}\)CO)\({}_{2}\)-H\({}_{2}\)O \\ \hline \hline \end{tabular}  
* S, synthetic; N, natural.  
\end{table} 
Table 1: _Cont._surface.