Between Bulhary and Salgótarján there are very young basalt mountains of the Pliocene-Pleistocene age (1.5-2.5 million years old), some of which were previously mined and are still exploited on the Slovak side. The cobbled streets of some cities are made of basalt cubes, for example, the cobblestones of Vienna were once made of basalt from Somoskő. Road metal is also produced from basalt for the construction of railway beds and asphalt pavements. In the cavities of basalts, a variety of minerals were formed from hot water solutions: various zeolites (phillipsite, natrolite, scolecite, offretite), carbonates (calcite, aragonite), and clay minerals (smectites).
In the picture: Aragonite, Bulhary (Slovakia). Image width: 7 cm. Photo by Sándor Szakáll.