A kaolin obtained from a region near to San Luis Potosí (México) was characterized by X-ray powder diffraction (DRX), optical microscopy (OM), scanning electron microscopy (SEM), X-ray fluorescence (XRF), thermal analysis (DTA/TGA), and chemical analysis. Mineralogical and morphological characteristics of the mineral are presented. The kaolin sample was formed mainly by kaolinite, but other minor phases were also detected such as quartz, cristobalite, trydimite, and dolomite. For iron lixiviation process, concentrate HCl was employed. The high content of volcanic glass detected, evidenced by optical microscopy, revealed an incomplete kaolinization process of the raw material. In agreement with these results, X-ray fluorescence analysis showed high- SiO2 and low-Al2O3 content in the sample as is expected on weakly kaolinized materials.