## 3 Results and Discussion  
### Mineralogy, Chemistry, and Morphology of the Palygorskite Sample  
The chemical composition of the palygorskite sample used is presented in Table 3.  
The presence of Si, Al, and Mg demonstrates that the sample is a magnesium-aluminum phyllosilicate. These are the main elements that constitute the chemical composition of palygorskites, which has the ideal formula MgAlSi\({}_{8}\)O\({}_{20}\)OH\({}_{3}\)(OH\({}_{2}\))\({}_{4}\).X[R\({}^{2+}\)(H\({}_{2}\)O)\({}_{4}\)], with X having the possibility to be replaced by Na, Fe, or Mn [22]. \begin{table}
\begin{tabular}{c c} \hline \hline
**Oxide** & **Percentage (\%)** \\ \hline Al\({}_{2}\)O\({}_{3}\) & 5.70 \\ SiO\({}_{2}\) & 50.97 \\ Fe\({}_{2}\)O\({}_{3}\) & 13.11 \\ MgO & 16.22 \\ Other Oxides & 2.08 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical composition of the palygorskite sample. Palygorskite commonly presents higher Al content, close to or greater than 10%, as can be observed in the results reported by [PERSON], [PERSON] et al., and [PERSON] et al. [23; 24; 25] that studied samples of this clay from Spain, Brazil, and China, respectively. However, for samples extracted from deposits located in Greece, such as the one used in this study, this content tends to be lower (close to or less than 5%). Regarding Al content, similar results to those presented in Table 3 were reported by [PERSON] and [PERSON], [PERSON] et al., and [PERSON] et al. [26; 27; 28]. Furthermore, a high Fe content was also identified (13.11%), which is also common for palygorskite samples from Greece, according to the works already cited. Thus, the chemical composition of the palygorskite used in this study is within the expected range. Regarding the mineralogical composition of the sample, the XRD pattern and the quantification of the identified phases are presented in Figure 1 and Table 4, respectively. Figure 1 illustrates the XRD pattern of palygorskite. The XRD pattern shows crystalline phases corresponding to the presence of palygorskite, antigorite, and quartz. These constituents were, respectively, identified using the crystallographic file numbers 75975, 98794, and 16331, provided by the Inorganic Crystal Structure Database (ICSD). It is possible to verify that the sample presented a sharp and symmetrical peak at 20\({}^{\circ}\), a value close to 8.50\({}^{\circ}\), which typifies the presence of the clay mineral palygorskite, and main peaks corresponded to the presence of impurities such as antigorite and quartz, close to 12.5\({}^{\circ}\) and 26.5\({}^{\circ}\), respectively, in addition to the identification of secondary peaks of these minerals. Quantification using the Rietveld method, as presented in Table 4, shows that this clay is rich in palygorskite, with more than 77% of the sample being made up of this clay mineral, as well as a minimal fraction of quartz corresponding to only 1.16%. Antigorite, on the other hand, presented a considerable fraction of 20.94%. Antigorite belongs to the serpentine group and has the ideal formula Mg\({}_{6}\)Si\({}_{4}\)O\({}_{10}\)(OH)\({}_{8}\)[29], which is in accordance with what was observed in the XRF analysis (Table 3). The presence of serpentines in palygorskite samples was also identified by [PERSON] et al., [PERSON] and [PERSON], and [PERSON] et al. [27; 28; 30]. Since the clay sample is mostly composed of palygorskite, it is expected \begin{table}
\begin{tabular}{c c} \hline \hline
**Phase** & **Percentage (\%)** \\ \hline Palygorskite & 77.90 \\ Antigorite & 20.94 \\ Quartz & 1.16 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Quantification of phases identified in XRD analysis. Figure 1: X-ray diffractogram of the palygorskite sample. P—palygorskite; A—antigorite; Q—quartz. that the properties of the investigated fluid formulations will be predominantly influenced by this clay mineral in comparison to antigorite or quartz.