This report presents an assessment of pyrite weathering on the chemistry of water in the abandoned Podwiśniówka quarry of the Holy Cross Mountains (south-central Poland). This quarry did not operate for ore minerals, but for quartzites. The area of the pit pond enlarges each year generally as a result of an influx of spring snowmelt or heavy rainfall. The water examined reveals a very low pH, varying from 2.27 to 3.57 (with geometric mean value of 2.90), and unusual low concentrations of cations and anions, especially total Fe (2.7–24.0 mg·L^-1) and SO₄^2- (55–285 mg·L^-1). With regard to its chemistry, this pond is unique compared to similar sites in Poland and even throughout the world. The low pH and element concentrations are attributed to the specific mineralogy of ore and gangue minerals, as well as complex bacterially catalyzed geochemical processes that have encompassed pyrite oxidation and iron oxidation/hydrolysis reactions.