Argentopentlandite has been found in samples collected on the dump of the Michael mine, an old silver mine in Zagórze Śląskie in the northern part of the Góry Sowie mountains. Though argentopentlandite is not a very common mineral, it is well known from high-temperature hydrothermal veins and from Ni-Cu deposits hosted in ultramafic rocks also containing platinum-group minerals. The argentopentlandite has been recognized in a sulphide nest in association with pyrrhotite and chalcopyrite in massive barite. In comparison to other occurrences (see Table 2), this mineral is characterized by a low Ni content (ave. 16.02wt% - EDS; 16.43wt% - WDS), a lack of cobalt and a relatively high copper content (ave. 2.13wt% - EDS; 1.55wt% - WDS). Based on these data, it can be concluded that the argentopentlandite, and the associated sulphides, were precipitated from hydrothermal fluids shortly after barite, the major vein constituent. As the optical properties of the argentopentlandite in reflected light are rather similar to those of bornite, it can be overlooked during routine observations. Thus, argentopentlandite or associated ore mineralization may also occur in other barite veins in the area.