# Mineralogical Transformations in Granitoids during Heating at Fire-Related Temperatures
## 2 Materials and Methods
### Materials Characterisation  
Polarizing Microscopy: Thin sections of the fresh granitoids were observed with a Nikon Labophot 2 polarizing microscope. Minerals were identified and quantified, and cracking patterns were characterized. SEM + EDX: Samples were observed with a scanning electron microscopy (SEM) Hitachi S3000N with an EDS detector BRUKER XFlash 3001 for microanalysis and mapping before and after heating at 1000 \({}^{\circ}\)C.  
FRX: Elementary chemical analysis was performed with an X-ray fluorescence device PHILIPS MAGICX PRO PW2400 on 30 g of powder of each fresh granitoid. The results were analysed with the SuperQ software to obtain an accurate quantification. In addition, mineral analysis was carried out with an Orbis Micro-XRF Analyzer EDAX. This technique and equipment allowed focussing analysis areas as small as 10 \(\upmu\)m and without the necessity to reduce the sample to powder. Thus, the minerals from the fresh and 1000 \({}^{\circ}\)C heated stones were analysed individually. Three measurement points were selected for each mineral and temperature and the average was calculated. XRD: Mineral composition was determined by X-ray diffraction. The equipment used was a Bruker D8-Advance with an X-ray generator KRISTALLOFELX K 760-80F  
Figure 1: Selected granitoids. (**A**): Eagle Red; (**B**): Grissal; (**C**): Golden Ski; (**D**): Negro Galicia. whose copper anode (Cu K alpha 0.15418 nm) allowed us to obtain the data in the 2 Theta interval 4-60\({}^{\circ}\). The results were treated with the software XPowder Ver. 2010.01.42 PRO. For the analysis, 30 g of powder from the sound stone were used. This equipment has a Goebel mirror, which allows a high temperature chamber to heat the sample and measure it simultaneously. Thus, each granitoid was heated up to 1000 \({}^{\circ}\)C and the XRD spectra analysed approximately each 200 \({}^{\circ}\)C. Chemical and structural variations were quantified and compared with bibliographical data for discussion of thermal expansion. XPS: Mineralogical transformations such as the oxidation state, binding energy of the different elements, and the concentration within the sample were analysed with X-ray photoelectron (XPS) AVG-Microtech Mutilab 3000 system equipped with a hemispherical electron analyser with nine channeltrons (with a step energy of 2-200 eV) and a X-RAY radiation source with Mg and Al anodes. A part of each granitoid was reduced to powder and measured. In addition, micas were separated and studied independently. Molar proportions of C, O, K, Fe, and Ti were selected as measurement parameters before and after heating. Five measurements were recorded in each sample. The detector quantifies the number of photoelectrons emitted by the sample after being triggered with the X-ray source. Its speed is related with the energy needed to extract them from the atom, termed as binding energy (BE). This energy is characteristic of each element. The BE value is also modified by the chemical environment of the atom that allows us to distinguish between species with different oxidation states. Because core level electrons in solid-state atoms are quantized, the resulting energy spectra exhibit peaks characteristic of the electronic structure of atoms in the sample. Linear thermal expansion: These coefficients (\(\alpha\)) were determined using a dilatometer and heating the samples from room temperature up to 90 \({}^{\circ}\)C with a \(\Delta\)T = 70 \({}^{\circ}\)C. The used dilatometer allows us to measure the deformation of six samples simultaneously, with a time interval of 20 s. The samples used were six cylinders of 50 \(\times\) 15 mm of each of the four granitoids, two of each direction of the space. The software used was DasyLab Voltmeter 5.6 [37]. Five cycles of heating-cooling were performed with the following steps. The linear thermal expansion was obtained from the average of the five cycles. * S1: Sample stabilization at 20 \({}^{\circ}\)C for 1 h.
* S2: Heating up to 90 \({}^{\circ}\)C with a constant rate of 1 \({}^{\circ}\)C/min.