Mines

Mining is the extraction of valuable minerals or other geological materials from the earth, usually (but not always) from an ore body, vein or (coal) seam. Materials commonly recovered by mining include bauxite, coal, copper, diamonds, iron (from haematite and limonite), gold, lead, manganese, magnesium, nickel, phosphate, platinum, salt, silver, tin, titanium, uranium, and zinc. Other highly useful materials that are mined include clay, sand, cinder, gravel, granite, and limestone. Any material that cannot be grown from agricultural processes must be mined. Mining in a wider sense can also include extraction of oil and gas.

History

The oldest known mine in the archaeological record is the "Lion Cave" in Swaziland. At this site, which has a radiocarbon age of 43,000 years, paleolithic humans mined for the iron-containing mineral hematite, which they presumably ground to produce the red pigment ochre.

Sites of a similar age where Neanderthals may have mined flint for weapons and tools have been found in Hungary.

Another early mining operation was the turquoise mine operated by the ancient Egyptians at Wady Maghareh on the Sinai Peninsula. Turquoise was also mined in pre-Columbian America in the Cerillos Mining District in New Mexico, where a mass of rock 200 feet in depth and 300 feet in width was removed with stone tools; the mine dump covers 20 acres.

Mining techniques

Mining techniques can be divided into two basic excavation types: 1) open-cast or open-pit mining and 2) tunneling by shafts into the earth.

• Open excavations
  • Open-pit mining
  • Quarrying
  • Strip mining
  • Placer mining

• Tunnel mines
  • Tunnel mining
  • Deep mining
  • Drift mining
  • Hard rock mining

Bioleaching is the application of bacteria to extract metals from an ore.

Environmental effects

Mining can have devastating impacts on the environment due to the massive rearrangement of minerals within the earth. The result can be unnatural high concentrations of some chemical elements over a significantly wider area of surface. Combined with the effects of water and the new 'channels' created for water to travel through, collect in, and contact with these chemicals, a situation is created where mass-scale contamination can occur.

Some examples of environmental problems associated with mining operations are:

Tar Creek, an abandoned mining area in Picher, Oklahoma that is now an Environmental Protection Agency superfund site. Water in the mine has leaked through into local groundwater, contaminating it with metals such as lead and cadmium.

Scouriotissa, a copper mine in Cyprus that has been abandoned. Contaminated dust blows off this site.

Berkeley Lake, an abandoned pit mine in Butte, Montana that has filled with water which is now acidic and poisonous.

See also

• Coal mining
• Acid mine drainage

References

• Tom Morrison. 1992. Hardrock Gold: A Miner's Tale (ISBN 0806124423)
• Geobacter Project: (in PDF format)