## 5 Results and Discussion
### Geochemistry  
Representative geochemical data for the surface of the tested materials are presented below (Table 4). They reflect the coexistence of silica and non-silica minerals in their bulk compositions. The concentrations of the majority of the main elements are comparative with those of the commercial product (S0, Table 4), as well as with similar products mentioned in the literature as being used for pelotherapy [31]. The percentages of the major silicon, calcium, and aluminum oxides detected were 44.03-45.41, 12.50-17.01, and 9.44-14.10 wt%, respectively, in the studied samples. Calcium ions participating mainly in carbonates, as well as in clay minerals, were spotted. However, even these increased percentages of calcium ions are likely to have a beneficial effect, with calcium participating in clay lattices, which can easily penetrate the skin during the pelotherapy treatment due to the  
Figure 8: SEM image showing (**a**) microcrystaline quartz with conjunctival fractures in microstructure of S1 sample and (**b,c**) fractured diatoms with clay minerals in S1 and S2 samples. high ion exchange ability of these minerals, contributing positively to the osteoporosis phenomena [57] and constituting a strong health problem for thousands of people. Lower amounts of iron (4.33-5.99 wt%), magnesium (2.98-3.96 wt%), potassium (1.95-2.31 wt%) and sodium oxide (1.19-1.34 wt%) complete the bulk oxide compositions of analyzed specimens. In regard to the trace elements, the analyses revealed increased concentrations of Ba (222-241 ppm), Zr (99-105 ppm), Sr (251-369 ppm) and Cr (177-220 ppm). As there are no established limits for element concentrations in natural mud materials used for cosmetic or other external therapeutic purposes, the analyses of this study compared well with those in the literature [31] as well as the S0 product. The results revealed that, in most cases, they are under acceptable levels when compared with the Canadian health products guides [53; 58]. Ba and Zr are characterized as elements with low risk for cosmetics, while Cr is classified as partially toxic if it exceeds the 1100 ppm in the bulk composition; this issue is something that does not occur in the analyzed samples. The limit values of Sr are not provided; however, it is characterized as a less hazardous element, while according to the guidelines high concentrations should be taken into account in peloid therapy. Combining the geochemical and mineralogical results, the relatively high concentrations of sulfur in S1 sample can be attributed to both the detected pyrite in framboids form and gypsum. Generally, sulfur rich peloids are strongly supported as treatment in skin conditions, such as psoriasis [59]. According to the European Regulation (Annex II) [60] and US Pharmacopoeia, the amount of Pb in clays should not exceed 40 ppm [61]. The average values (ppm) relative to Pb of each sample were compared with these reference values in order to understand to what extent the concentration of the metal exceeds this limit. According to the standards of the Pharmacopoeia, the levels of Pb remain within the acceptable limits, since they are all lower than 40 ppm (Table 4).