Pit lakes have been one of the most adopted forms of decommissioning open-pit mines after the mineral resource has exhausted, so that a proper use is given to these areas. These lakes are usually narrower and deeper when compared to natural lakes, being almost always surrounded by steep rocky walls. The aim of this work is the analysis of the hydrogeochemical variations of a pit lake formed in an abandoned steatite pit. The lake, even if relatively shallow, is clearly stratified, showing a monomictic behavior, with circulation of water only in cold months (June, July, August and September). The OPPS pit lake can be classified as a tropical hot, monomictic lake. Despite relatively young and shallow (maximum depth of 28 m), the lake is totally stratified, with a clear evolution from stratified to destratified along the year, with water circulation occurring during the colder months (mainly July, August and September). The lack of convection flows in ca. 2/3 of the year makes the re-aeration of the lake difficult, leading to the maintenance of reducing conditions in the hypolimnion. A pH between neutral and alkaline is maintained in the pit lake, which leads to a better quality of the water in the lake.