Acid mine drainage
![Yellow boy in a stream receiving acid drainage from surface coal mining.](/Images/godic/202501/27/Iron_hydroxide_precipitate_in_stream5816.jpg")
![Rocks stained by acid mine drainage on Shamokin Creek](/Images/godic/202501/27/Rocks_on_Shamokin_Creek5816.JPG")
![In this case, the pyrite has dissolved away yielding a cube shape and residual gold. This break down is the main driver of acid mine drainage.](/Images/godic/202501/27/GoldinPyriteDrainage_acide5816.JPG")
![Rio Tinto in Spain.](/Images/godic/202501/27/Rio_tinto_river_CarolStoker_NASA_Ames_Research_Center5816.jpg")
Acid mine drainage, acid and metalliferous drainage (AMD), or acid rock drainage (ARD) refers to the outflow of acidic water from metal mines or coal mines.
Acid rock drainage occurs naturally within some environments as part of the rock weathering process but is exacerbated by large-scale earth disturbances characteristic of mining and other large construction activities, usually within rocks containing an abundance of sulfide minerals. Areas where the earth has been disturbed (e.g. construction sites, subdivisions, and transportation corridors) may create acid rock drainage. In many localities, the liquid that drains from coal stocks, coal handling facilities, coal washeries, and coal waste tips can be highly acidic, and in such cases it is treated as acid rock drainage.