Characteristics of Neogene clay materials in Northwest Bulgaria – new data for the areas near Bela and Staropatitsa villages

Clay materials have a variety of unique characteristics and have various applications in many industries. In this paper, we represent new data about the mineralogical and chemical characteristics of the Neogene clay materials from the areas of the villages of Bela and Staropatitsa, Northwest Bulgaria. The phase composition of the samples mainly consists of quartz and clay minerals, which in both sites are represented by smectite and kaolinite types, with mica, chlorite, illite, and potassium feldspars present. The chemical analysis indicated that silica and alumina were predominant in the analyzed samples, with medium contents of iron oxide. The percentage of MgO, K₂O, and TiO₂ content is explained by the presence of montmorillonite minerals, illite/mica, and anatase. The high values of the Chemical Index of Alteration (CIA) show that the clay materials underwent intense alteration. Further research into the chemical and mineralogical properties and the technical parameters of these clay materials is critical for understanding their formation processes, assessing their industrial applications, and improving the geologic and geotechnical assessments related to environmental implications.