Krušnohoří is the name of a mountain range, the Krušné hory, the ore mountains. It is the southern part of an area which is cut into two pieces by the German-Czech border. On the German side it is named Erzgebirge, which translates ore mountains.
The mining started in the 16th century, at that time both parts were German speaking, so even on the Czech side most towns and mines have German names. The polymetallic ores were ideal for labor intensive manual mining, but high grade, which means easy to process. Also they were easy to discover, the miners simply followed the ores they found on the surface underground.
The hills were formed during the variszian orogeny and subject to weathering since then, so only a rather low hill country, the core of the mountain range still remains. The metamorphic rocks have ore veins, which are a result of a granite intrusion, which caused the cracks and filled them through hydrothermal convection. The ores are polymetallic, a bunch of sulfur based metal ores, mostly tin, zinc, copper and silver, sometimes gold, sometimes uranium. The ores are together with quartz and baryte.
The mining region Erzgebirge/Krušnohoří was inscribed into the UNESCO World heritage list in 2019. In preparation of the inscription and as a result several Medieval mines were opened to the public as show mines.