Acid mine water

1. Mine water that contains free sulfuric acid, mainly due to the weathering of iron pyrites. A pit water, which corrodes iron pipes and pumps, usually contains a high proportion of solids per gallon, principally the sulfates of iron, chiefly ferrous and alumina. See also: acid water
2. Where sulfide minerals break down under chemical influence of oxygen and water, the mine drainage becomes acidic and can corrode ironwork. If it reaches a river system, biological damage may also result. Pryor, 3
   Source: Dictionary of Mining, Mineral, and Related Terms