Characterization of Mg-calcites from marbles of the Mediterranean area

Mg-rich calcites from marbles of the Mediterranean area were accurately characterized by Rietveld X-ray powder diffraction (XRPD) and X-ray fluorescence (XRF) for the determination of the Mg content of the samples. The data set seems to be highly consistent, despite the different metamorphic environment under which calcite grains have formed. Results indicate that previously reported determinative curves, regarding synthetic Mg-calcites, relating the c/a ratio to the Mg content of the carbonate, do not hold for these natural inorganic samples which display an ideal, or nearly ideal, behaviour of the calcite - dolomite solid solution for compositions between 0 and 4 % mole MgCO3.