Mercury (element) long periods at elevated temperatures. It reverts to the elements upon heating near 400 °C, as was demonstrated by Joseph Priestley in an early synthesis of pure oxygen. Hydroxides of mercury are poorly characterized, as they are for its neighbors gold and silver. Being a soft metal, mercury forms very stable derivatives with the heavier chalcogens. Preeminent is mercury(II) sulfide, HgS, which occurs in nature as the ore cinnabar and is the brilliant pigment vermillion. Like ZnS, HgS crystallizes in two forms, the reddish cubic form and the black zinc blende form. The latter sometimes occurs naturally as metacinnabar. Mercury(II)
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