Open-cast mining of rock materials provides many essential resources for industry and construction; however, it also significantly impacts the natural environment surrounding the mining sites. The most severe environmental threats posed by open-cast mining of rock materials include land occupation and often associated deforestation, changes in the hydrological regime of the area, emissions of gaseous and particulate pollutants into the atmosphere, noise emissions, and many others. This study aimed to investigate the extent and scope of the impact of a quarry located in southern Poland on the growth and degree of defoliation of trees in the surrounding forest ecosystem, and to examine how dust deposition on the forest floor changes. Additionally, the study examined how the quarry affects the development of natural forest regeneration and the species composition of ground vegetation. For this purpose, two 140-meter transects were established in the field, divided into four plots, with the centers located at 10, 50, 90, and 130 meters from the quarry edge. On these plots, the diameter at breast height (DBH) and height of the trees were measured, and their degree of defoliation was assessed. The understory trees were inventoried (divided into three height categories), and the contents of Al and Fe (in addition to silicon, these elements are present in diabase in the highest concentrations) in the litter was determined to assess dust deposition. Furthermore, phytosociological surveys were conducted in the plots, and each plant was assigned an appropriate light indicator value (Ecological Indicator Value). The study showed significant differences in the concentrations of Al and Fe in litter between plots, and a clear decreasing trend in the concentration of these elements with increasing distance from the quarry was observed. Trees closer to the quarry had smaller DBHs and a higher degree of defoliation. The phytosociological surveys indicated that the light requirements of plants increased with distance from the quarry. Overall, this study found that open-cast mining activities affected the surrounding forest ecosystems, and that the greatest threat posed by the quarry operations was the dust deposition on the forest floor. This phenomenon could possibly be significantly reduced by implementing a properly shaped ecotone zone.