Tailings are the waste and by-products generated by mining operations. The tailings seen here were pumped into the Gribbens Basin, next to the Empire and Tilden Iron Ore Mines in Negaunee, Michigan, USA. Once the materials are pumped into the pond, they are mixed with water to create a sloppy form of mud known as slurry. The slurry is then pumped through magnetic separation chambers to extract usable ore and increase the mine's total output. For a sense of scale, this Overview shows approximately 2.5 square kilometres (1 square mile) of the basin.