Geoheritage of the Precious Opal Bearing Zone in Libanka Mining District (Slovakia) and Its Geotourism and Geoeducation Potential

The northern part of the Slanské Vrchy Mountains, in Slovakia, within the territory of Dubnik Opal Mines, is considered to be the historical source of opal, including the opal known to the Romans. Dubnik precious opal mineralization originating from post-magmatic hydrothermal fluids based on its values should be recognized as an area of global importance. Geological processes that are connected to Neogene volcanic activity took place in the territory of the Dubnik Opal Mines and resulted in the formation of various geological products and processes represented by polymetallic mineral formation, opal formation, antimonite formation, and mineralization of the supergene stage, as well as the stratovolcano rock environment, which are of geoheritage significance. Remnants of intensive mining activity that took place during the past 2000 years provide opportunities for visitors to explore, study, and appreciate this unique geological heritage of international importance. However, geo-interpretation aimed at the general public (the largest group of potential visitors from sustainable geotourism development) and research on (geo)tourism and/or geoheritage for tourism purposes, as discussed in this paper, are lacking.