Mining and Environment Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Mining is the removal or extraction of rocks, minerals, ores, gemstones, or other geological materials from the earth, typically from an ore body, seam, or vein. Mined materials include diamond, iron, tin, bauxite (aluminum), precious metals (gold, platinum, silver), lead, nickel, and rocks like coal, limestone, marble, salt, and uranium. Mining can also include the extraction of petroleum, natural gas, and water.

The earliest known mine operated 43,000 years ago in Swaziland, Africa, where iron ore (hematite) was removed and ground into a red pigment called ochre. Other early operations mined turquoise in ancient Egypt and in pre-Columbian America in Cerrillos, New Mexico. The first mining operation to use gunpowder was in Slovakia in 1627.

Surface Mining

Mining techniques can be divided into two basic extraction types: surface and subsurface. Surface mining removes or extracts deposits of rocks and minerals that are near the surface. First, the land is prospected to locate rock, minerals, and ores. The extent and value of ore is determined and the quality of the material is estimated. A feasibility study is conducted to valuate the proposed mining project. Access to the ore is established to extract and remove the important rock. In large commercial operations, heavy equipment like backhoes and earthmovers first remove the overburden (the soil, gravel, or rock above the valuable deposits). Next, huge backhoes called tower or dragline excavators extract the mineral and redeposit the materials into trucks or onto conveyer belts. Then it is taken away to be crushed further and/or to be extracted from attached rock (gangue). Finally, the land is reclaimed to make the mined environment suitable for use again.

Surface mining results in the production of large piles of waste rock called spoil banks, until the area is recovered through mandatory mitigation policies. Because surface mining techniques remove overlying material, large portions of the countryside may be altered, and the mining operation often destroys the local ecosystem.

There are five techniques for surface mining. Open-pit mining removes rocks or minerals from an open pit because the material is close to the surface and the overburden is thin or the earth is unstable for tunnels. Strip-mining is similar to open-pit mining and extracts ore by removing all overburden. It is a practical technique when the ore is near the surface. Strip-mining generally leaves spoil banks until the area is reclaimed. This technique can have enormous negative environmental effects. Quarrying uses shallow open pits for removing building materials, such as limestone, marble or granite.

Placer mining is accomplished using water pressure (hydraulic mining) or surface excavating equipment to separate and remove materials in alluvial or loose deposits of sand and gravel in stream beds where the material is typically unconsolidated and cannot be tunneled.

Natural processes have separated the valuable materials from the original veins or deposits through stream action, weathering, or erosion and they can then be extracted from stream beds where their greater density permits separation using running water in sluices or pans. This technique was particularly effective during the California Gold Rush in the 1850s and is used today for gem mining in Southeast Asia and gold mining in the Yukon, Alaska, and British Columbia. Because of the large amounts of sediments that are disturbed, placer mining is considered environmentally destructive, so many placer mines now use settling ponds to capture these silts.

Mountaintop removal is a relatively new form of mining in which the earth is destroyed or restructured to reach deep rocks and minerals (less than 1,000 feet [305 meters]). It often requires the complete removal of all timber (clear-cutting) to level the mountain with explosives. In many cases in the United States, this destructive practice has been ruled illegal by the Clean Water Act (1972).

Subsurface Mining

Underground or subsurface mining uses techniques to remove or extract valuable minerals, ores, or other geological materials from beneath the surface, involving equipment and/or miners that work underground. Greater risks are involved with underground mining because the overburden is not removed but lies above. Subsurface coal mines, for instance, are commonly at risk to fires smoldering for years since they can be nearly impossible to control or extinguish.

There are four types of underground mining. Shaft mining uses shafts or tunnels that are vertical or inclined. On the surface above the shaft lies the pithead or hoist and winding apparatus that raises and lowers the cage within the shaft. This cage carries minerals, miners, and equipment. Drift or slope mining cuts into the side of the earth, rather than tunneling downwards. This technique creates access to the material (e.g., coal seams) at slanted or horizontal angles. Hard-rock mining techniques are used to mine ore bodies by digging underground rooms or stopes that are supported by timbers or pillars of standing rock. Hard rock mining is used to extract ores that include gold, zinc, copper, and diamonds. Borehole mining remotely extracts minerals through the use of boreholes and high pressure water and can be used in hillsides, open pits, underground mines, or from floating platforms. Currently the world’s deepest mines are for gold extraction and exceed 12,000 feet (3,658 meters).

In 2005, there were nearly three million jobs in the American mining industry and extracted materials were valued at about $30 billion per year or nearly 4 percent of the U.S. Gross Domestic Product.

Bibliography:

Alena Mudroch et , Remediation of Abandoned Surface Coal Mining Sites: A NATOProject (Springer, 2002);
Earle A. Ripley and Robert E. Redmann, Environmental Effects of Mining (CRC, 1995).