## 3 Results and Discussion
### Bricks  
The mineralogical and petrographic characteristics of the brick samples coming from side 4 of the inner dome are summarized in Table 5. XRPD data show the presence of quartz, calcite, and plagioclase in all of the examined samples; muscovite is identified in samples 1A and 1D, traces of diopside were identified in sample 1B, and K feldspar in sample 1A. All of the detected minerals can be ascribed to raw materials used for the production of bricks, with the exception of diopside, which can nucleate for the reaction between carbonates and clay materials [21; 41; 42]. The coexistence of this newly formed mineral and calcite is quite a common occurrence, although the latter is not stable at high temperatures. Its presence can be explained by considering a secondary recrystallization due to the movement of Ca-rich solutions in the walls.  
Concerning the petrographic characteristics, two typologies have been identified: the first one (samples 1A and 1B) is characterized by a red colored paste (Figure 11a). The groundmass has a low birefringent with a medium amount of framework (ratio groundmass/framework 1/2). The framework is composed of quartz, plagioclase, and K  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Brick Samples** & **Groundmass** & **Framework** & **Macroporosity** & **XRD Data** \\ \hline \multirow{4}{*}{1A} & \multirow{4}{*}{Low birefringence} & Composition: quartz, micas, plagioclase & Quartz ++ \\  & & and k feldspar & Low, presence inside the & Calcite * \\  & & Well sorted & pores of recrystallization & Plagioclase + \\  & & Grain size 150–300 μm & of calcite & K feldspar * \\  & & Shape: sub rounded/sub angular & & Muscovite * \\ \hline \multirow{4}{*}{1B} & \multirow{4}{*}{Low birefringence} & Composition: quartz, micas and & \multirow{4}{*}{Medium} & Quartz ++ \\  & & plagioclase & & \\ \cline{1-1}  & & Well sorted & & \\ \cline{1-1}  & & Grain size 150–300 μm & of calcite & Plagioclase + \\ \cline{1-1}  & & Shape: sub angular & & \\ \hline \multirow{4}{*}{1C} & \multirow{4}{*}{Low birefringence} & Composition: quartz, plagioclase, & \multirow{4}{*}{Medium} & Quartz ++ \\  & & carbonate rock fragments & & \\ \cline{1-1}  & & Medium sorted & & \\ \cline{1-1}  & & Grain size 150–500 μm & & \\ \cline{1-1}  & & Shape: sub angular & & \\ \hline \multirow{4}{*}{1D} & \multirow{4}{*}{Low birefringence} & Composition: quartz, micas, plagioclase, & \multirow{4}{*}{Medium} & Quartz ++ \\  & & carbonate rock fragment & & \\ \cline{1-1}  & & Grain size distribution (bimodal) & & \\ \cline{1-1}  & & 150–200 μm 1–2 mm & & \\ \cline{1-1}  & & Shape: sub rounded/sub angular & & \\ \hline \hline \end{tabular} ++: very abundant; ++: abundant; +: present; *: traces.  
\end{table}
Table 5: Mineralogical composition (semiquantitative data) and petrographic description of bricks.  
fieldspar. The maximum grain size of the framework's components is 300 \(\upmu\)m, the texture is not oriented, and secondary recrystallization of calcite in macroporosity is observed. The second typology (samples 1C and 1D) has a light red colored paste, and more abundant framework (ratio groundmass/framework 1/3) made of quartz, micas, plagioclase, and carbonate rock fragments (micritic limestones) (Figure 11b). The framework is not well sorted and selected. A bimodal grain size distribution was observed for sample 1D. A medium macroporosity was registered.  
Thermoluminescence (TL) dating [14; 43] of these samples revealed two different ages: 4 th-5 th century, and around the 20 th century.  
The first date is probably linked to the re-use of most ancient bricks, while the 20 th century must be considered a post quem term for the building of the structure. The limited number of samples analyzed and dated cannot be considered exhaustive of the resolution of the chronological problematics in such a complex building.  
A specific research project devoted to these materials would be desirable.