Tailings
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In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction of an ore. Tailings are different from overburden, which is
Yellow boy in a stream receiving acid mine drainage from surface coal mining
Phosphogypsum stack located near Fort Meade, Florida. These contain the waste byproducts of the phosphate fertilizer industry.
Red mud near Stade (Germany)
Bauxite, an aluminium ore (Hérault department, France). The reddish colour is due to iron oxides that make up the main part of the red mud.
Acid mine drainage
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Acid mine drainage, acid and metalliferous drainage, or acid rock drainage is the outflow of acidic water from metal mines and coal mines.
Tailings
…coal. Although harmless underground, these minerals are reactive toward air in the presence of microorganisms, which if not properly managed lead to acid mine drainage. Between 100 million and 280 million tons of phosphogypsum waste are estimated to be produced annually as a consequence of the processing of phosphate…
Rio Tinto in Spain presents an acid drainage of both natural and artificial origin (mining)
Rocks stained by ferrous precipitate from acid mine drainage on Shamokin Creek in Northumberland County, Pennsylvania
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.