Leopold Jan Szersznik (1747–1814) – a Silesian priest, teacher, researcher and collector, was a leading figure in the Age of Enlightenment. He is known mainly as a founder of a great and commonly available library of manuscripts, ancient books and maps, and one of the first Polish public museums. The Szersznik’s Museum was founded in 1802 in Cieszyn to collect art, antique weapons, instruments and nature specimens, forming so-called Naturalienkabinet. Naturalienkabinet contained more than four thousand minerals, rocks and fossils. The collection was designed to illustrate the natural history and was characterised by excellent systematization and description of type, place of origin and number of specimens. Szersznik planned to create a full catalogue of natural history collections, but unfortunately he could not finish his project. The only remaining part of the mineralogical collection is stored at the Museum of Geology of Deposits in Gliwice (Poland), being one of the oldest geological collections in Poland. Unfortunately, the state of preservation and arrangement of collections at the time of their transfer to the Museum was far different from its original state. The collection has been inventoried and described scienti- fically in recent years. Among the studied geological specimens are both well-known rocks and minerals from classic locations and unusual mineralogical specimens.