mining

Miners studying a map in an underground mine.

An open pit, or opencast, copper mine. This mine is in Arizona, USA, which produces more than half of the US annual output of copper. Until the latter part of the 20th century copper was only second in importance and use to iron, but by the 1960s it had been replaced by aluminium, which was much more easily accessible, and cheaper.

Pendarves tin mine, Cornwall. Tin has been mined in Cornwall for thousands of years, but the Cornish tin-mining industry peaked during the 19th century, and has since declined. Foreign competition in the 20th century made Cornish ore increasingly unprofitable. The last working mines, including this one at Pendarves near Camborne, closed a few years ago. A few sites have been reopened as heritage centres.

Cornish tin miners in the pit. Illnesses such as bronchitis, consumption, and rheumatism were common among the men who worked underground, and by the age of 40, many miners were no longer fit to work. Death and injury were accepted hazards of the job. The Cornish tin mines did, however, inspire several safety-based innovations, such as the miner's safety lamp, invented by Penzance-born Humphry Davy.

Extraction of minerals from under the land or sea for industrial or domestic uses. Exhaustion of traditionally accessible resources has led to the development of new mining techniques, for example extraction of oil from offshore deposits and from land shale reserves. Technology is also under development for the exploitation of minerals from entirely new sources such as mud deposits and mineral nodules from the seabed.

Mud deposits, for example, are laid down by hot springs (about 350°C/660°F): sea water penetrates beneath the ocean floor and carries copper, silver, and zinc with it on its return. Such springs occur along the mid-ocean ridges of the Atlantic and Pacific and in the geological rift between Africa and Arabia under the Red Sea.

Likewise, mineral nodules form on the ocean bed and contain manganese, cobalt, copper, molybdenum, and nickel; they stand out on the surface, and ‘grow’ by only a few millimetres every 100,000 years.

The deepest mine in Europe is a 1,100 m/3,610 ft deep working salt and potash mine at Boulby near Whitby on the northeast coast of England.

mining

In warfare, military term meaning to drive a tunnel beneath an enemy position. The end of the tunnel is filled with explosives which are then detonated so as to destroy the position and its occupants.

The technique was frequently employed on the Western Front during World War I, but its drawback was that the enormous crater created could often be defended by unharmed troops quicker than the attackers could reach it.