New Almaden hydrothermal deposition of cinnabar from deep within the earth is found in a gangue of silica-carbonate rock formed locally by hydrothermal alteration of serpentine. The Guadalupe mine produced about 10% as much mercury as the New Almaden. There are several smaller mines in the mining district, but their ore production was not significant. The only significant quicksilver ore is cinnabar; other sulfides are present in small quantities. Mining, other than a single placer deposit of cinnabar, was underground. There is a high probability of undiscovered high-grade ore which could be found and exploited using modern techniques. Mining operations resulted in
Ore Mountains sharply defined because the Ore Mountains, a typical example of a fault-block, descend very gradually. The topographical transition from the Western and Central Ore Mountains to the loess hill country to the north between Zwickau and Chemnitz is referred to as the Ore Mountain Basin; that from the Eastern Ore Mountains as the Ore Mountain Foreland. Between Freital and Pirna, the area is called the Dresden Ore Mountain Foreland ("Dresdner Erzgebirgsvorland") or Bannewitz-Possendorf-Burkhardswald Plateau ("Bannewitz-Possendorf-Burkhardswalder Plateau"). Geologically the Ore Mountains reach the city limits of Dresden at the Windberg hill near Freital and the Karsdorf Fault. The V-shaped valleys of