This paper deals with the effects of modifications to clay-siliceous raw material from Dylągówka (Dynów foothills, SE Poland), which alter the rheological properties of its water suspensions. The investigations were carried out on three samples collected from various depths of the deposit as they considerably differ in their contents of smectite and other minerals. The samples were either modified with soda or activated with sulphuric (VI) acid and used to prepare their water suspensions with various contents of solids. The suspensions were subject to determinations of viscosity and flow curves. Dependencies of three variables of the suspensions (rheological properties, mineral composition of the solid phase, and the modifications introduced) were assessed on the basis of: the contents of the solid phase in the suspensions required to obtain a viscosity of 1000 mPas; hypothetical, calculated thixotropic energy. These show that the amount of solids in the water suspension required to obtain the required viscosity is considerably lower in samples with higher contents of smectite and in those activated with sodium. In turn, the acid activation that partially alters smectite towards a protonated silica gel decreases the viscosity and thixotropy of the suspensions, which was confirmed in the studies of mid-infrared spectroscopy. The conducted studies provide important information needed in designing the mineral composition of drilling fluids and others applications.

The rocks quarried in the neighboring Rutki and Ligota Tułowicka deposits (vicinity of Niemodlin) represent a single petrographic variety of basalt, i.e. nephelinite. The presence of nepheline (the mineral belonging to the group of feldspathoids) that forms the light-colored component of the groundmass is the characteristic feature of these rocks. Nepheline is accompanied by fine crystals of pyroxene and, occasionally, magnetite. Distinctly larger pyroxene and olivine phenocrysts are dispersed within the groundmass. Neither minerals of the groundmass nor the phenocrysts of the pyroxenes reveal any signs of chemical weathering. However, such alterations are clearly visible in the phenocrysts of olivine. The basalt raw materials of both deposits are utilized mainly for the production of various assortments of crushed road aggregates and as components of concretes. These applications require the aggregates with the grain sizes >2 mm. There is also a possibility to utilize coarse-grained basalt aggregates for the manufacturing of rock wool. This is due to a favorable property of the rocks from Rutki and Ligota Tułowicka that is their relatively low content of magnetite resulting in the low capability of the molten basalt to crystallize. The chemical weathering of the olivine phenocrysts have proceeded toward the formation of clay minerals, among which those of the smectite group prevail. Their elevated quantities occur in the finest aggregate assortment, i.e. 0–0.85 mm. The fineness of this grain fraction and its elevated quantity of clay minerals are two favorable features to utilize this part of the basalt aggregate by the heavy clay industry as an additive improving the physico-mechanical parameters and providing the required red color of ceramic products..