The Jurassic kaolinite-illite clays in Rozwady (Opoczno region) were exploited for the needs of the chamotte fireclay refractories plant in Opoczno built in the years 1926–1928. Until the World War II, these clays were a major component of ceramic sets used for manufacturing quartz-chamotte refractories applicable to steel-making ladles in the Upper Silesian steel works. In the year 1990, due to a drastically low demand for chamotte refractories in Poland, both the plant in Opoczno and the Mroczków-Rozwady clay underground mine were shut down. However, recent years have brought about a renewed interest in exploiting the Opoczno clays for the domestic ceramic industry. Clay mining was initiated in 2014 in the new open pit in Borkowice and has also continued as of 2017 exploiting the Rozwady I deposit. In the clay raw material of Rozwady, kaolinite clearly predominates over illite, among the non-clay minerals quartz occurs in variable quantities, whereas the organic matter is a permanent but minor component. The quantity of the organic matter varies within the deposit and forms the basis to distinguish light and dark colored clays. Considering the petrographical reasons, the raw material of Rozwady represents rocks intermediate between claystones and mudstones. The Rozwady clays have been used by many plants producing tiles within the Opoczno region and it is predicted that their use will increase, as the prices of the clay raw materials imported from Ukraine is constantly growing and the cost of their transport is substantial.
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..