## 3 Results and Discussion  
### Mineralogical, Chemical and Petrophysical Characteristics of the Stone  
The stone, being massive and granular in appearance, is not very compact, with a high porosity and a medium-low density, and exhibits a thin altered layer or surface crust. It is white to light beige (N9 to 10 YR 8/2, Munsell rock color chart) with dark mottling in the altered surface area.  
XRD analysis showed a predominant calcite mineral composition (90-95%), as well as dolomite (5-10%). Analysis of the surface of the sample by \(\upmu\)XRD also revealed the presence of calcite as the main constituent, and other accessory minerals, such as thenardite (NaSO\({}_{4}\)) and hematite-type iron oxides (Fe\({}_{2}\)O\({}_{3}\)).  
The stone is a medium- to coarse-grained oolitic/peloidal limestone. According to the most used limestone classifications, it would be classified as oopelsparite [4] and oolitic/peloidal grainstone [5]. It is composed of medium- to coarse-sized (0.15-1 mm), rounded to sub-rounded grains that show poor sorting (Figure 3), developing a grain-supported fabric with point, long and concave-convex contacts between the grains (Figures 3 and 4A).  
Highly mcritized ooids and peloids (85-95%), ranging from 150 to 750 \(\upmu\)m in size, (Figures 3 and 4) are the predominant framework constituents. Echin, molluscs and foraminifera fragments of highly variable size were also observed, reaching 2 mm thick in some cases (Figure 3A-D). The bioclasts showed a good state of conservation in the case of echinoderm plates and are quite micritized in the rest of bioclasts (Figures 3 and 4). Non-carbonate grains are very scarce, mainly consisting of small grains of silicate (Figure 3F) or iron oxide minerals. A very scarce interstitial matrix (micrite) between framework grains was observed. The main cement types recognized were micro- and mesocrystalline calcite cements, showing both continuous circumgranular and occluding (syntaxial, mosaic, poikilotopic) geometries in intergranular positions, corresponding to different cement phases (Figures 3C-F and 4A). Micro-mesocrystalline cements partially filling intraparticle pores (Figure 3C,D), and microcrystalline cements filling fractures or veins (10-25 \(\upmu\)mthick) (Figure 4B) were also observed. Locally, some microcrystalline siliceous cement was recognized in an interparticle position (Figure 3F).  
Figure 3: Optical photomicrographs. (**A**–**C**) General view of the sample showing a grain-supported fabric with framework composed of ooids, peloids and bioclast fragments, all of them bound by intercrystalline calcite cements. (**D**,**E**) Interparticle and intraparticle calcite cements between grains showing point, long and concave–convex contacts. (**F**) Detail of altered silicate grain and microcrystalline siliceous cement. (**A**–**E**) Plane polarized light. (**F**) Cross polarized light.  
The porosity of the sample is relatively high (5-15%) and fabric selective, mainly with interparticle and intercrystalline pore types. Framework grains (ooids, biochasts) showed severe micritization processes (Figures 3 and 4). Most of the ooids appeared as rounded micritiic grains that locally presented relics of primary microstructures (laminae,  
Figure 4: Optical photomicrographs. (**A**) Interparticle and intraparticle calcite cements between grains with point, long and concave–convex contacts. (**B**) Detail of a fracture filled by microcrystalline calcitic cement. (**C**) General view of the surface alteration crust. (**D–F**) Detail of the surface alteration crusts (see text). (**A–E**) Plane polarized light. (**F**) Cross polarized light.  
banded, internal chambers). The sample showed evidence of mechanical and/or chemical compaction (long and concave-convex contacts) (Figures 3D,E and 4A), as well as fracturing (Figure 4B).  
The surface alteration crust showed a variable thickness (20-100 \(\upmu\)m) (Figure 4C-F), a compact texture, a predominantly very small crystal/grain size (<25 \(\upmu\)m), and a greater abundance of oxides.