## 2 Materials and Methods  
The nineteen pigments studied were supplied by Kremer Pigments GmbH & Co. KG (Aichstetten, Germany): silicates (Egyptian blue, natural and synthetic blue ultramarine, green earth and chrysocolla), oxides (natural and synthetic hematite, red and yellow natural ochres, and chromium green), carbonates (natural and synthetic azurite, natural and synthetic malachite, and white lead), sulphides (natural and synthetic cinnabar, and orn) and acetates (verdigris). The data provided by the supplier for each pigment are included in Table 1.  
\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{5}{*}{ \begin{tabular}{c} \#100601 \\ Egyptian blue \\ \end{tabular}  } & \multirow{2}{*}{EGB-S} & \multirow{2}{*}{Cuprioviate} & \multirow{2}{*}{Cuprioviate, CaCuSi\({}_{4}\)O\({}_{10}\)} \\  & & & & Quartz, SiO\({}_{2}\) \\ \cline{5-5}  & & & & Lazurite, Na\({}_{3}\)Ca(Al\({}_{3}\)Si\({}_{3}\)O\({}_{2}\))S \\  & & & & Sodalite, Na\({}_{3}\)Al\({}_{5}\)Si\({}_{3}\)O\({}_{2}\)Cl\({}_{2}\) \\  & & & & Calcite, CaCO\({}_{3}\) \\  & & & & Diposide, CaMgSi\({}_{2}\)O\({}_{6}\) \\  & & & & Pyrite, Fe5 \\  & & & & Alpite, (Na\({}_{3}\)Ca)(Si,Al)\({}_{4}\)O\({}_{3}\) \\  & & & & Muscovite, KAl\({}_{3}\)Si\({}_{3}\)Al\({}_{5}\)O\({}_{10}\)(OH)\({}_{2}\) \\  & & & & Wollastonite, CaSiO\({}_{3}\) \\ \cline{5-5}  & & & & Lazurite, Na\({}_{3}\)Ca(Al\({}_{3}\)Si\({}_{3}\)O\({}_{2}\))S \\ Silicates & \begin{tabular}{c} \#45010 \\ Ulramarine \\ \end{tabular}  & UL-S & \begin{tabular}{c} Sodium aluminium \\ sulphosilicate + kaolinite \\ \end{tabular}  & \ \begin{tabular}{c} Sadalite, Na\({}_{3}\)Al\({}_{5}\)Si\({}_{3}\)O\({}_{2}\)Cl\({}_{2}\))S \\ Scadolite, Na\({}_{3}\)Al\({}_{5}\)Si\({}_{3}\)O\({}_{2}\)Cl\({}_{2}\))S \\ Scadolite, Na\({}_{3}\)Al\({}_{5}\)Si\({}_{3}\)O\({}_{2}\)Cl\({}_{2}\))S \\ Scadolite, Na\({}_{3}\)Al\({}_{5}\)Si\({}_{3}\)O\({}_{10}\)(OH)\({}_{4}\) \\ \end{tabular}  \\ \cline{5-5}  & & & & Glauconite, (K\({}_{3}\)Na)(Fe\({}^{+}\)Al,Al\({}_{3}\)Si,Al)\({}_{4}\)O\({}_{10}\)(OH)\({}_{2}\) \\  & & & & Celadolite, K\({}_{3}\)MgFe\({}^{+}\)Si\({}_{3}\)O\({}_{10}\)(OH)\({}_{2}\) \\  & & & Muscovite, KAl\({}_{3}\)(Al\({}_{5}\)Si\({}_{3}\)O\({}_{10}\))(OH)\({}_{2}\) \\  & \#11010 & & & Calcite, CaCO\({}_{3}\) \\ Green Verona & GE-N & \multirow{2}{*}{Celadonite} & \multirow{2}{*}{Clinochore, (Mg,Fe\({}^{+}\))\({}_{3}\)Al(Si\({}_{3}\)Al)O\({}_{10}\)(OH)\({}_{8}\)} \\ earth & & & & Alpite, Na\({}_{3}\)Si\({}_{3}\)O\({}_{8}\) \\  & & & & Monformillonite, \\  & & & & (Na\({}_{3}\)Ca)\({}_{3}\)(Al,Mg)\({}_{3}\)Si\({}_{3}\)O\({}_{10}\)(OH)\({}_{2}\)\({}_{10}\)(OH)\({}_{2}\)\({}_{10}\)H\({}_{2}\)O \\  & & & & Kaolinite, Al\({}_{3}\)Si\({}_{3}\)O\({}_{5}\)(OH)\({}_{4}\) \\ \cline{5-5}  & & & & Chrysocolla, CuSiO\({}_{3}\) \\ Chrysocolla & CHR-N & Natural copper silicate & \multirow{2}{*}{Malachite, Cu\({}_{3}\)O\({}_{5}\)Cu(OH)\({}_{2}\)} \\  & & & & Quadrite, SiO\({}_{2}\) \\ \hline \multirow{5}{*}{ \begin{tabular}{c} \#48651 \\ Hematite \\ Iron oxide red \\ \end{tabular}  } & \multirow{2}{*}{HE-N} & \multirow{2}{*}{Natural iron oxide + SiO\({}_{2}\) +} & Hematite, Fe\({}_{3}\)O\({}_{3}\) \\  & & & Quartz, SiO\({}_{2}\) \\  & & & & Aquartz, SiO\({}_{2}\) \\ \cline{5-5}  & & & & Gypsum, CaSO\({}_{4}\)\(\cdot\)2H\({}_{2}\)O \\  & & & & Diposide, CaMgSi\({}_{2}\)O\({}_{6}\) \\  & & & & Illite, (K,H\({}_{3}\)O)(Al,Mg,Fe)\({}_{2}\)(Si,Al)\({}_{4}\)O\({}_{10}\)[OH]\({}_{2}\)(H\({}_{2}\)O) \\ \cline{5-5}  & & & & & Goethite, FeO(OH) \\ \cline{5-5}  & & & & Calcite, CaCO\({}_{3}\) \\ \cline{5-5}  & & & & \\ \cline{5-5}  & & & & & Calcite, CaCO\({}_{3}\) \\ \cline{5-5}  & & & & \\The mineralogical composition of the powdered pigments was determined using X-ray diffraction (XRD) with an XPert PRO PANalytical B.V. (Almelo, The Netherlands), according to the random-powder method.