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One of the most known sedimentary formation among Egyptian Upper Cretacous rock units is named Duwi Formation (Lower Maastrichtian), an outcrop at the Abu Tartur plateau, Kharga Oasis, Western Desert Egypt. This formation displays three montmorillonitic clayey layers. The investigations of these sediments provide information on the texture, constituents and type of clay minerals, which helps define and describe their physical and technical properties.

Granulometrically, the selected samples have siltstone, mudstone and claystone facies. Mineralogical analysis of the studied deposits proved that the clay minerals compose mainly of montmorillonite, in addition to small amount of glauconite, and traces of illite. Scanning electron microscopy revealed three main micro-structures, namely honeycomb, matrix, and turbulent.

Acid activation of eight samples was performed using hydrochloric acid. The efficiency of activation was examined by measuring their bleaching capacity to crude cotton seed oil, and changes in their surface areas. The acid treatment resulted in more than 4-fold increase in the activity of the pretreated bentonite samples. The extent of activation was found to be pronounced after the first 30 minutes of acid treatment.