## 3 Results
### XRF Analysis  
In order to obtain qualitative information on the chemical composition of the investigated samples, XRF measurements were carried out on various painted areas of the fragments, as well as on the wall painting plasters. The results of the XRF analysis are summarized in Table 1. As expected, and in accordance with the FTIR data, all areas investigated show intense Ca lines (Figure 5), most probably associated with calcite. In order to avoid the layering effect, all samples were measured on the decorated surfaces and also on the back. Taking into account the measurement setup and the penetration depth of the primary X-rays, the calcium contribution partially comes from the pigmented layer, and partially from the plaster used as a substrate. Trace amounts of Sr were also found in all the investigated areas, most probably due to the substitution of Ca by Sr in the calcite crystal structure [39]. In terms of key elements that can be associated with the used pigments, all pigmented areas show high amounts of Fe, and for some of the areas, also of Mn, which indicate the presence of iron and manganese-rich ochres [37]. Copper and other various trace elements such as Ti, As, Hg, Cr, and Zn can be linked with impurities present in the ones used for the manufacturing of pigments [40]. However, the chemical fingerprint of the pigments may have been affected by the burial environment as well. As shown in other studies [41], prolonged burial can lead to different enrichments of leached metals of the soil that determine a change within the original elemental composition of the pigment. Si, which was also found, can be linked with the presence of some common silicates, namely, quartz, as confirmed by FTIR, that accompany the bulk pigment. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample** & **Typology** & **Color/Typology** & **Detected Elements** \\ \hline S1 & paint layer & red with black & **Fe, Ca,** Mn, Cu, Ti, Pb, K, Hg, Zn, S, Sr, Si, P \\ S2 & paint layer & red & **Ca, Fe, Mn, Cu, Ti, K, Pb, S, Si, Zn, Hg, Sr** \\ S3 & paint layer & yellow, red, and black & **Ca, Fe, Mn, Sr, K, Cu, Pb, Ti, Zn, Si, S, Rb, Cr, Al** \\ S4 & paint layer & red with black & **Ca, Fe, Mn, Sr, K, Ti, As, Zn, Pb, Cu, Si, Rb, S, P** \\ S5 & paint layer & red with yellow & **Ca, Fe, Mn, K, St, Ti, Pb, Cu, Zn, Si, Cr, Rb, S, P** \\ S6 & paint layer & white with yellow & **Ca, Fe, Mn, Sr, Pb, Cu, Ti, Ba, Zn, S, Si, Rb, P, Al** \\ S7 & paint layer & black & **Ca, Mn, Fe, Cu, Ti, Pb, Si, S, Sr, Zn** \\ S8 & fine plaster layer & white & **Ca, Fe, Sr, Mn, Cu, Ti, Cu, Ti** \\ S9 & coarse plaster & greyish-white & **Ca, Fe, K, Mn, Rb, Ti, As, Sr, Cu, Si** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of the XRF analysis. Identified elements are shown in order of decreasing abundance (major abundant elements are marked in bold; trace elements are marked in italics). An aspect that stands out from the XRF data is that, compared to all other samples, sample S7 (black pigment) is characterized by an inversed Mn/Fe ratio: while the general tendency was for more iron as compared to manganese, for the black pigment sample, it appears to be exactly the opposite, as illustrated in Figure 6. This would suggest the use of a manganese-containing black pigment, possibly a manganese (di)oxide, which can be found in black ochres [42]. On the contrary, similar samples analyzed from the site of Ulpia Traiana Sarmizegetusa all had more iron as compared to manganese [6]. For each sample, the substrate was also analyzed (Figure 5), indicating Ca as a major component, along with a smaller input of Fe and Mn, which can be associated with calcite impurities, as it is known that Mn\({}^{2+}\) ions can substitute for Ca\({}^{2+}\) ions in marbles [43]. Additionally, minor traces of terrigenous materials were evidenced, such as K, S, and Ti. Figure 5: XRF spectra of representative samples (S1—red and black; S2—red; S3—white and yellow; S7—black). Figure 6: Manganese versus iron ratio for all pigment samples.