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Purpose. Determination of the thermal effect (combustion) on the geochemical characteristics of waste rock argillite, and on the leachability of pollutants for establishing the potential of these compounds as a source of drainage and groundwater pollution. Methodology. The article describes the investigation of argillite, the main component of the basin’s waste heaps, the analysis of pollutant leaching from unburned and burned argillite using a washing plant, their X-ray fluorescence analysis, the surface morphology of different types of argillite by scanning electron microscopy (SEM), the qualitative and quantitative composition of samples using energy dispersive X-ray spectroscopy (EDS) and the content of water-soluble heavy metals by atomic absorption. Findings. As a result of thermal effects on argillite, the salt content in the washing water increases by 2.5 times and reaches 185 ppm in water from unburned rock and 462 ppm from burned rock, the sulfur content in the burned rock after washing decreased by 21.3 times. The variability of changes in the content of water-soluble compounds in the studied samples is also noted, since the amount of Mn, Pb, Cu and Co leached out is up to 15.5 times higher in unburned argillite, but the amount of Fe and Zn leached out after combustion increases up to 17.4 times compared to unburned rock. Originality. The series of changes in the content of chemical elements and compounds as a result of combustion and rock washing have been established, which are important for assessing and predicting the migration potential of chemical elements from coal dump rocks to soils and waters within coal spoil tips. Practical value. The conducted research characterises the ecological state of spoil tips and can be used for reclamation or melioration works in these areas, taking into account the degree of rock metamorphism. [ABSTRACT FROM AUTHOR]