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Open-pit Mine

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Mining Processes
An Open Pit Copper Mine near Winkleman, Arizona
An open-pit mine is a mine that resides at the ground’s surface from which ore can be extracted. Although the mine is an open pit, some excavation is required. Open-pit mines are used to extract ores such as coal, copper, gold, iron, and aluminum.

When an open-pit mine is developed, there are a number of environmental, safety, and cost-related factors to consider, including noise and air quality and animal habitats.[1]

Other names for an open-pit mine include open-cast, open-cut, and strip mine.

[edit] Process

The mine operation is developed by first establishing a bench, also known as a ledge, which enables miners to strip away layers. Benches are typically 13 to 197 feet (4 - 60 m) in depth. Stripping shovels are required to strip away the overburden that blankets the ore, which normally takes place on an angle derived from the bench. Each layer of the bench begins to resemble a step, continuing as far down as ore can be extracted. Overburden generally consists of thin rocks that are unsuitable for tunnels, where the top layers can easily be removed to access the valuable ore.

Other shovels and excavators are used to dig into successive layers and break the ore into manageable bits so that it can be loaded into dump or haul trucks and taken to a processing site, usually on-site. Some rocks may be too hard to be excavated in the traditional manner, so blasting and drilling methods are relied upon to complete the job. Underground mines are built when minerals cannot be accessed from the surface. These types of mines usually require the construction of tunnels.[2]

Open-pit mines are enlarged until the resources are exhausted or until the cost of operating them exceeds the profit. When this occurs, open-pit mines are abandoned, and will either become the site of a landfill or a pond.

Sometimes, if an open-pit mine is deep enough, mining is taken underground; machinery is sent underground via vertical mine shafts.[3]

[edit] References

  1. Open Pit Surface Mine. Mine-Engineer.com, 2008-09-29.
  2. Open Pit Surface Mine. Mine-Engineer.com, 2008-09-29.
  3. Open-pit mining. De Beers, 2008-09-29.