Geosite. Open for the public.
Szilvás-kő is a groups of mesas that consist of three basalt cones (Bago-kő 579 m, Szilvas-kő 628.1 m, Kis-Szilvas-kő 620 m), which are all situated in Ronabanya belonging to the town of Salgotartjan, Hungary.
The basalts following the main tectonic direction of the area form a ridge of SSE-NNW orientation, which stands out high of its surroundings. The eruption could have taken place at several stages 3.8 to 2.2 million years ago. This is buttressed by the stratfication of "fresh" lava rock, and hiatal-breccia lava and lapilli tuff. Bago-kő is the remainder of a lava flow that filled up an erosion ditch. It is interesting that there are thin columns perpendicular to one another on the northern wall of the Bago-kő basalt mine (G40). Such columns come to being at the place where both lateral and bottom cooling surfaces meet with the inside of a lava flow.