Detailed multi-scale characterization of the kaolin quality and the controlling depositional environment is crucial for optimal quality upgrading and for prioritizing potential exploitation areas. In the present work, the quality of El-Tih kaolin, Egypt, was investigated using the chemical/mineralogical characteristics as well as the field observations of the clay. Chemical analysis of major oxides was carried out using energy dispersive X-ray fluorescence (EDS-XRF) spectrometry. Mineralogical analyses were carried out using X-ray diffraction (XRD) and scanning electron microscopy coupled with wavelength-dispersive X-ray spectroscopy (SEM-WDS). Spatial heterogeneity of the quality was evaluated applying kriging geostatistical techniques and potential zones were identified.
Results clarified an upward gradual deterioration of the quality via a decrease in the Al2O3 content and thickness of the clay layers, and an increase in the TiO2 content. According to the kriging maps, areas of high potentiality indices (PI) characterized by high Al2O3 and low SiO2 content and maximum thickness of the kaolin are located to the west and east, and decrease toward the central part of the study area. The high PI zones are dominated by pseudo-hexagonal platy kaolinite, often forming accordion- and book-like aggregates with subordinate quartz and traces of Fe and Ti oxides, yielding minimal TiO2 and Fe2O3 contents. These zones of high PI are considered optimal for exploitation. Kaolinite was formed as a result of intensive weathering of rhyolite/granite and basalt in the source area, and subsequent erosion, transportation and deposition of the weathering mantles in a flood environment with marked depositional energy variations. Results allowed comparison with worldwide kaolin occurrences, and suggested the suitability of the studied kaolins for use in paper coating and filling and in higher-grade ceramics, after removal of free Fe- and Ti-oxide impurities.