## 2 Materials and Methods
The classification and description of dolomitic textures was performed according to Gregg and Sibley [27] and [PERSON] [28] for the nomenclature of dolomite crystal sizes. Petrographic analyses were accomplished on 150 samples, corresponding to all the sections (outcrops, quarries and boreholes) studied and representative of all the textural types that constitute the ME commercial marble. Thin sections were obtained by standard methods and observed under a Zeiss Axiscop microscope for definition of compositional and textural features. Potassium ferricanide and alizarin red \(S\) staining method was used distinguishing between carbonate minerals [29]. The mineral composition of the samples was determined by X-ray diffraction (XRD) using a Phillips PW1710/00 diffractometer (30 kV, 25 mA), using CuK\(\alpha\) radiation (1.54054 A), in the XRD Laboratory of the Department of Geology of the National Museum of Natural Sciences (MNCN-CSIC, Madrid, Spain). For the calculation of % mol MgCO\({}_{3}\) of the different carbonate phases, the methods of Goldsmith and Graf [30] and [PERSON] et al. [31] were applied, using quartz as an internal standard and measuring the position of the d(104) peak of the carbonate phases. To establish the degree of ordering of the dolomite crystals, the intensity ratio between 015 and 110 peaks was used [32]. Major-element and minor-element concentrations were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) at ACME Analytical Laboratories (Vancouver, Canada) and by means of X-ray fluorescence (XRF) MNCN Laboratories (CSIC, Madrid, Spain). The list of the analysed elements can be consulted in Tables S1 and S2(Supplementary Materials). The samples were introduced into the spectrometers once pulverised, compacted and pressed to perform a qualitative and semi-quantitative analysis with a series of standards to calibrate any element. Loss on ignition or calcination (LOI) was obtained by calcining the sample in a flask up to 1000 \({}^{\circ}\)C and maintaining this temperature for 1 h, and for a series of samples with a small amount of sample, automatic thermogravimetry/differential thermal analysis (TG/DTA) equipment was used. In the ornamental rock manufacturing industry, the determination of colour is a key aspect for the classification and employability of rocks. The colour determination of the different stone samples was carried out through the use of [PERSON]'s Rock Colour Chart, both in the field and in the laboratory, and the use of a Minolta CR300 colourimeter. With the colourimeter, colours were measured in the form of three variables: L* (lightness), a* (red/green colour component) and b* (blue/yellow colour component), using the CIELAB measurement method (International Commission on Illumination). This technique was used in circular samples, with a diameter of 60 mm and a thickness of 20 mm, which are perfectly adapted to the measuring equipment, thus avoiding the entry of external light. For the calculation of the chromatic differences (total colour, \(\Delta\)E) we used the following expression [15; 33; 34]:  
\[\Delta\mathrm{E}=\sqrt{(\Delta\mathrm{L})^{2}+(\Delta\mathrm{a})^{2}+(\Delta \mathrm{b})^{2}} \tag{1}\]  
To adapt the colour determinations, the Munsell system was used to carry out statistical calculations; a conversion of H V/C (hue value/chroma) Munsell Colour Coordinates under illumint C to Cie-L*a*b* System was performed [35; 36; 37].