2019-5-10 · Mercury occurs naturally in the environment and exists in a large number of forms. Like lead or cadmium, mercury is a constituent element of the earth, a heavy metal.In pure form, it is known alternatively as "elemental" or "metallic" mercury (also expressed as Hg(0) or Hg 0).Mercury is rarely found in nature as the pure, liquid metal, but rather within compounds and inorganic salts.