## 5 Results
### Petrophysical Properties
The sandstone showed a much lower value of 1.81 \(\pm\) 0.13 g/cm\({}^{3}\), as well as the \"sandstone\" _s.l._ samples, in which there was an average value of 1.92 \(\pm\) 0.05 g/cm\({}^{3}\)  
Figure 13: (**a**) Bulk density ((\(\rho_{\rm B}\)) vs. PLT index (Is(\(\rho_{\rm 0}\))); (**b**) helium open porosity (\(\Phi\) He) vs. PLT index (Is(\(\rho_{\rm 0}\))). (Table 2). The marly limestone, given their low porosity, showed a high bulk density value of 2.60 g/cm\({}^{3}\). Metasilstone had bulk and real densities of 2.19 and 2.70 g/cm\({}^{3}\) (Table 2), respectively, and thus represented one of the lowest values among the metamorphic rocks. The real density, which is mainly influenced by the mineralogical composition, and only to a limited extent by the possible closed porosity (not determined here), showed distinct values between metadolostone and sandstone. In the former, due to the strong presence of the dolomite phase (with a density of 2.84 g/cm\({}^{3}\)) and secondly of calcite (2.71 g/cm\({}^{3}\)), this property varied from 2.75 \(\pm\) 0.04 g/cm\({}^{3}\) in breciated metadolostone, to 2.76 \(\pm\) 0.04 g/cm\({}^{3}\) in massive metadolostone, to 2.79 \(\pm\) 0.05 g/cm\({}^{3}\) in laminated metadolostone. While sandstone, due to the prevalent presence of quartz (2.65 g/cm\({}^{3}\)), K-feldspar (2.54-2.56 g/cm\({}^{3}\)), abundant fossils (2.65-2.71 g/cm\({}^{3}\)), and only subordinate of phases with high density (e.g., calcite deriving from the \"cement\" of the matrix), showed a lower average value, equal to 2.73 \(\pm\) 0.01 g/cm\({}^{3}\) (Table 2). The \"sandstone\" _s.l._ samples were characterized by the lowest real densities, ranging between 2.46 and 2.60 g/cm\({}^{3}\), with an average value of 2.55 \(\pm\) 0.05 g/cm\({}^{3}\) (Table 2). This is likely due to the lime-based artificial binder which, during the carbonation process of Ca(OH)\({}_{2}\) to form CaCO\({}_{3}\) (by CO\({}_{2}\) capture from the atmosphere), developed a significant amount of intraphase closed microporosity that affected the volume measurement. The marly limestones, due to a different mineralogy mainly characterized by carbonate phases, organic compounds and low presence of clay, had the lowest average real density compared to all other samples, probably due to the greater presence of microporosity closed to helium (not interconnected). The compactness coefficient (C), calculated as the ratio between the bulk density and the real density, inversely proportional to the porosity, was quite homogeneous among the three lithotypes of metadolostone as evidenced by the average values of 0.92, 0.87, 0.88, respectively (Table 2), while the sandstone samples, due to a decidedly higher porosity than the metadolostone samples, showed lower compactness index values, with an average value of 0.66. The artificial \"sandstone\" _s.l._ samples, due to their different composition, had an intermediate average value between the previous values, equal to 0.75 (Table 2). Marylimestones, due to their very low porosity (<4%), showed the highest compactness index (0.96). Metasilstone had a C value of 0.81, the lowest among metamorphic rocks. Among the hydraulic properties, the coefficient of imbibition expressed in weight (IC\({}_{\rm W}\)) followed the trend shown by the porosity open to water (Figure 12a), with which a clear positive correlation, with values respectively of 3.2 \(\pm\) 2.5%, 4.7 \(\pm\) 1.5%, 4.2 \(\pm\) 1.1% for metadolostones, and 15.5 \(\pm\) 4.2% for sandstone (Table 2) was found. Artificial \"sandstone\" _s.l._ had a value of 10.2 \(\pm\) 1.2%. The marly limestones, having a low open porosity, showed a low value of the imbibition coefficient (1.2%) compared to the other average values observed. The porosity closed to water, calculated as the difference between the absolute values of open porosity to helium and to water, had quite high values in sandstone and synthetic \"sandstone\" _s.l._, respectively of 5.9 \(\pm\) 1.9%, 4.9 \(\pm\) 1.2% (Table 2).