## 2 Materials and Methods
Isotopic analyzes (\(\delta^{13}\)C, \(\delta^{18}\)O) were carried out on powders of marbles using a mass spectrometer (Finnigan MAT Delta Plus) equipped with Finnigan Gas-Bench II. Sample and standard mineral powders were treated with phosphoric acid for 1 h in sealed glass containers previously flushed with helium. The CO\({}_{2}\) produced was introduced into the mass spectrometer in continuous flow mode, using helium as carrier. The gas from the sample was run along the with reference CO\({}_{2}\) gas of a known composition. The experimental values were normalized against international (NBS-18) and internal standards. The mean external reproducibility was better than 0.1 for \(\delta^{13}\)C and \(\delta^{18}\)O.  
Fourier-transform infrared spectroscopy (FT-IR) was performed for the determination of patina and encrustations through a spectrometer Alpha Bruker. The acquisition of spectra was carried out directly on site by using the instrument equipped with the external total reflectance module for a contactless acquisition and a video camera. Spectra were collected in the range of 7000-400 cm\({}^{-1}\) at a resolution of 4 cm\({}^{-1}\) and 128 scans in order to optimise the signal-to-noise ratio, on a 4 mm diameter area. FT-IR analysis of powders were conducted, instead, with the ATR (attenuated total reflectance) configuration. The acquisition was carried out in the spectral range between 4000 and 400 cm\({}^{-1}\), with a resolution of 4 cm\({}^{-1}\) for 24 scans. All of the acquired spectra were elaborated using the OPUS 7.2 software by [PERSON]. A micro-chemical analysis of red and yellow patinas was carried out with a Renishaw single-grating (1200 grooves/mm) RM2000 micro-Raman spectrometer and charge-coupled device (CCD) air-cooled (577 \(\times\) 400 pixels) detector. Spectra were recorded using a near infrared diode laser (785 nm) employed as an excitation source. Laser beam focusing was accomplished through a 50\(\times\) magnification objective that provided a 1.5 um laser spot diameter. Neutral density filters were used to attenuate the laser power in order to avoid phase transformations. The laser power at the analyzed samples was within the range 1-2 mW. The spectral range investigated was between 200 and 2000 cm\({}^{-1}\). Acquisition times were in the order of 30 s, and the spectral resolution was 4 cm\({}^{-1}\) for the diode laser. Thermo-gravimetric analysis (TGA) was employed for binder characterization of mortars. Some fragments of each sample were disaggregated using a porcelain pestle, and the fraction passing through a sieve with 63 um openings (ISO R 565 Series) was considered as a binder-enriched specimen. TGA was used to evaluate the presence and the amount of particular volatile compounds (essentially H\({}_{2}\)O, CO\({}_{2}\)) in the samples. TGA was conducted in the range 110-1000 \({}^{\circ}\)C on approximately 5 mg of sample, and dried (silica gel as drying agent) at room temperature for at least a week under the following experimental conditions: open alumina crucibles, heating rate of 10 \({}^{\circ}\)C/min, and 30 mL/min nitrogen gas flow. TGA was used for classifying the studied samples as hydraulic or non-hydraulic mortars, as suggested by most authors [23; 24; 25]. TGA analyzes were performed using a Perkin Elmer Pyris 6 system on mortar samples. A list of different types of materials analyzed and of methodologies applied for each material are reported in Table 1.