## 4 Multi-Analytical Methods
In [7; 8], NDT techniques (ultrasonic pulse velocity and Schmidt hammer tests) were used to obtain accurate and reliable information of the state of conservation and mechanical characterization of the stone. NDT measurements and data gathered from optometric surveys, including a detailed photographic campaign, were attributed to each individual element, and directly on-site was inserted into a database through a custom mobile app. Instrumental data and vector and CAD data, obtained from the architectural survey, were then processed through GIS software ESRI ArcMap 10.7 using a relative reference system composed of plane coordinates xy. The processing in GIS allowed us to produce thematic maps useful for reading the results, upgradeable and integrable over time [3; 41]; the GIS project is also prepared for interoperability with building information models (BIM). In addition to the NDT tests, few destructive tests (DT) involving the sampling of the most representative block types were carried out to complete the characterization of the material through the petrographic and mineralogical features of the investigated rocks. Rock samples were collected with a core drill system (HILTI DD 150-U) with a 2.5 cm diameter. Drilling was performed on the most representative Pietraforte blocks, selected on the basis the above-mentioned NDT results, trying to collect the natural rock discontinuities and their homogeneous neighbors. Core depths varied from 2 to 4 cm depending on the hardness and the consistencies of the drilled blocks. The samples are described and prepared to determine the physical properties as water accessible porosity Pw (%), apparent density d (g/cm\({}^{3}\)), and imbibition coefficient IC (%) using a hydrostatic balance [7; 42]. Core samples were oven dried and cut to obtain the maximum number of slices from the top to the bottom of the drilled cores, then prepared for scanning electron microscopy (SEM, EVO-MA15 Carl Zeiss AG, Milan, Italy) coupled with energy dispersion spectroscopy microanalytical system (EDS, Oxford Instruments, Wiesbaden, Germany) investigation. A feature identification module included in the image analysis software (AZTEC, Oxford Instruments, Wiesbaden, Germany) was used to map the distribution (and for the calculation) of the sample porosity over a representative portion of each sample. Elemental maps were also produced through EDS on the same areas to highlight their geochemical distribution. After SEM-EDS analysis, thin sections of the obtained slices were prepared for petrographic investigation (ZEISS Axio Scope.A1 polarized light optical microscope, OM, with software AxioVision). Multi-analytical procedures have been selected with the aim of gathering the advantages of each technique: an architectural survey, critical optometric survey of the stone characteristics, and NDT measurements were conducted over the entire surface to monitor and assess the stone decay. NDT tests and the database collected allowed us to summarize the characteristics of the individual elements and to select the samples of natural discontinuities to investigate the petrographic, mineralogical, and physical features of rocks and their contribution to the state of conservation.