## 3 Results
### Characterization of the Reference Panel
This hypothesis finds a double confirmation in Figure 4C, obtained by deleting the 9.2 keV peak, Pb L\({}_{\text{I}}\) line: firstly, the similarity distribution of sequence 4 approaches that of 3 and, in addition, the removal of 9.2 keV line also affects 11, 14, and 17, which contain red ochre \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Panel** & **A** & **B** & **C** & & & **D** & & \\ \hline
**Ranking (q)** & 0 & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\ \hline
**Energy (keV)** & & 10.5 & 12.6 & 9.2 & 13.8 & 8.8 & 6.4 & 11.8 & 10.0 & 11.3 \\ \hline
**X-ray transition** & \begin{tabular}{c} L\({}_{\alpha}\) \\ (Pb) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\beta}\) \\ (Pb) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{I}}\) \\ (Pb) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{J}}\) \\ (Hg) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{I}}\) \\ (Hg) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{J}}\) \\ (Fe) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{I}}\) \\ (Hg) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{K}}\) \\ (Hg) \\ \end{tabular} & \begin{tabular}{c} L\({}_{\text{B}}\) \\ (Hg) \\ \end{tabular} & \
\begin{tabular}{c} L\({}_{\text{K}}\) \\ (Hg) \\ \end{tabular} &
\begin{tabular}{c} L\({}_{\text{I}}\) \\ (Hg) \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The principal energies (i.e., elements’ emission series) emerging from the GS relating to the reference panel data. The series has been ordered following their abundance from the most to the less detected. The energy of the emission has been reported in keV and classified according to the X-ray nomenclature. The letters refer to Figure 4 and specify the series that have been removed before the calculation of the corresponding set of similarity maps. too. It must be noticed that, after deleting the 3 rd series of the ranking, a slight change can be observed for all the multi-layers as could be expected for a peak belonging to Pb. Even if \(\left[A\right]_{k_{3}}\) do not suggest relations between sequences 7 and 8 (both containing Red Ochre; 7 below, 8 above Cinnabar) and the Hematite/Red Ochre group, the similarity maps of Figure 4C can be definitively grouped into 3 sets related, respectively, to Red Lake, Cinnabar and to the couple Hematite/Red Ochre. Once Iron has been eliminated (\(\left[A\right]_{k_{6}}\), Figure 4D) Hematite/Red Ochre's group vanishes since it loses its peculiarity. The Red Lake set behaves in the same way probably because of the absence of Fe, a condition which marks this group and that, without the channels referred to Iron, stops to be significant. Summarizing, STEAM discerns three principal sets within the sequences of the reference panel dominated, respectively, by Hg, Fe, and the absence of Fe. Moreover, kept out the comments about 7 and 8, every consideration about the sequences of these samples' results is reliable also with any a priori knowledge of the reference panel' layers. The behavior of 7 and 8 is probably due to the shading action of Hg over Fe; thesis which finds prompt confirmation by manually switching the removal order for Iron and Mercury. If the 10 keV L\({}_{\alpha}\) and the 11.8 keV L\({}_{\beta}\) of Hg are removed before the 6.4 keV K\({}_{\alpha}\) of Fe (\(\left[A\right]_{k_{6}}\), Figure 4E) the Cinnabar group vanishes, 7 and 8 reveal the presence of Fe, and their similarity maps can be associated with the Hematite/Red Ochre's group. Simultaneously, 2, 10, 13, 15, 16, 18, and 19 lose their signature and assimilate to the Red Lake's group consistently with the fact that Cinnabar itself does not contain Iron. The same conclusions can be inferred by changing the STEAM's ranking criterion from abundance to incidence. Figure 5 shows what happens using as ranking's rationale the number of pixels involved by a significant similarity change (greater than the 10% in terms of image brightness) after the removal of one of the detected X-ray series.