Opencast mining, also called "opencut mining," or "open pit mining," is based on the principle of continuous conveying, employing large earth-moving machinery such as the Big Muskie walking dragline to mine the coal, iron ore or phosphates at the surface rather than underground. Opencast mining may include multi-seam mining, where two or more coal seams are excavated. The advantage of opencast mining, as opposed to underground, mining is that it is generally easier, cheaper, safer and quicker to bring onstream (into production).

Opencast mining of coal is carried out as these giant machines; including the bucket-wheel excavator, stripping shovel, steam shovel, slusher and walking dragline; strip away the overburden until the coal seam is reached. This form of mining often employs the use of mud caps, or other explosive devices to periodically break up the deposit of ore using this conventional drill-and-blast method. The drill-and-blast method may be single-row blasting involving driling, charging and firing a single row of holes along the opencast face; or multiple-row blasting which involves multiple blasts often in a square pattern along the opencast face.

The overburden can then be removed in trucks or by railway to the processing mill. The coal once extracted is then transported to a area to be sorted, broken and cleaned using coal benefication techniques. Crushing usually involves the use of a push feeder, jaw crusher, rotary breaker, discard bins and conveyors. Once processed the ore is graded for sale.

During the opencast mining process terraces, or benches are formed along the earth often leaving ugly gaping holes, often the overburden is backfilled to mined out areas on a continuous basis. Once the coal runs out the area is either abandoned, used for a landfill, or returned to its orignal state through reclaimation.

A panoramic view of an opencast mine can be seen at:
http://zbyszek.strefa.pl/panoramy/kopalnia/me.html

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