[Abstract] Mineralogical, geochemical and XRD microstructural characterization for different groups of argillized materials of the Iberian Massif have been performed; the variability and correllation of these characteristics has been analyzed trhough statistical procedures by onsidering hierarchic cluster analisys and geological attributes. One of the clusters established within the studied materials is made up of material (kaolins) with kaolinite as main component. The profile parameter FWHM of the 001 reflexion, for kaolinites and illites (when the mineral was abundant enough to obtain adecuate profiles in the oriented agregates) as well as the microstructural parameters supplied by the Mudmaster program has been studied . A more accurate microstructural study to compare the aparent cristallite size parameter obtained with different methods (Voigt Function, Warren – A verbach and Mudmaster program) has been developed for a set of selected samples. The XRD aparent crystallite size data has been compared with those obtained through FESEM (working at high magnification). An interpretation of crystal growth mecanisms in studied kaolinites has been performed through analysis of XRD microstructural data.