# Itarare Group Sandstone as a Sustainable Alternative Material for Photon Radiation Shielding
## 4 Discussion  
The study presented here aimed to demonstrate that even minor changes in the chemical composition of sandstone samples can have a significant impact on their radiation shielding properties. The density of each sample was determined using the volumetric balloon method, which involved powdered rock samples, resulting in values ranging from 1.51 to 1.64 g/cm\({}^{3}\). Therefore, the method used to measure the density of the samples takes into account the space between the particles and not just the particle density, for which the measured relative density was 2.53. Our values are lower than those reported by [PERSON] et al. [18] and [PERSON] et al. [26], which can be attributed to the porosity of the materials analyzed. Differences in chemical composition due to the origin of the rocks also explain the lack of agreement between studies. Samples RMPI and RMPP exhibited the highest sandstone densities, indicating lower porosity. Although the mineralogical composition was not addressed in our study [27; 28], which also influences sample density, our results highlight the importance of considering both chemical composition and structural characteristics when evaluating the shielding efficiency of natural rocks. However, it is essential to note that our study does not present experimental measurements, which would allow for a more in-depth exploration of the structural characteristics of the samples, such as the influence of porosity on attenuation. Our study presents a theoretical analysis of the shielding parameters based on data from the samples' chemical composition and density. The chemical composition of the samples is predominantly made up of silicon and aluminum oxides, with SiO\({}_{2}\) being the major component, accounting for 66% to 74% of the weight. In rocks like sandstones, it is typical to find a high concentration of SiO\({}_{2}\)-rich minerals, such as quartz [29]. Smaller quantities of other elements were also detected, including Fe\({}_{2}\)O\({}_{3}\), K\({}_{2}\)O, and TiO\({}_{2}\). [PERSON] et al. [30] reported that Fe\({}_{2}\)O\({}_{3}\) levels range from 1.08% to 3.49% by weight, TiO\({}_{2}\) from 0.01% to 0.27%, and K\({}_{2}\)O from 1.37% to 1.97%, which are comparable to the findings of our study. Furthermore, the research by [PERSON] et al. [31] also indicates a predominance of SiO\({}_{2}\) in sandstone's composition; however, the Al\({}_{2}\)O\({}_{3}\) content they measured was nearly half of what we found. Still, the values for Fe\({}_{2}\)O\({}_{3}\), K\({}_{2}\)O, and TiO\({}_{2}\) reported in their study align closely with our results. Other research on Brazilian sandstones from various formations has yielded results that are consistent with our findings, as well [28; 29]. The results presented in Figures 3 and 4 indicate that the mass attenuation coefficient and linear attenuation coefficient were influenced by the chemical composition of the samples [32]. At the lowest photon energies, samples with higher Fe\({}_{2}\)O\({}_{3}\) content, such as RMPS and RMPI, demonstrated superior attenuation performance compared to samples like AR2. The higher density values listed in Table 1 for these samples help explain their increased LAC, especially at lower energies (0.015 and 0.1 MeV). This behavior is primarily due to the dominance of photoelectric absorption mainly at the lowest photon energies, where the chemical composition--particularly the presence of high atomic number elements, like iron--and density play a crucial role in photon attenuation. In contrast, aluminum and silicon oxides had minimal impact on the rocks' attenuation properties. As shown by [PERSON] et al. [33], elements like iron have a high capacity for photon attenuation at low energies. [PERSON] et al. [13] also reported a positive correlation between MAC and Fe\({}_{2}\)O\({}_{3}\) content, along with an inverse relationship between MAC and SiO\({}_{2}\) content for photons with energy levels around 0.06 MeV.