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Minerals

Minerals are the substances rocks are made of. The solid outer layer of the earth's crust is made up of many kinds of rock, each consisting of one, or a combination of minerals. The main materials extracted from the earth are metals and minerals.

Mineral deposits are found all over the earth's surface. They are extracted from the land by open-cast and underground mining. Extraction of minerals has been going on for over 2.5 million years when Neolithic people excavated rocks such as flint out of the ground to make tools.

Minerals include limestone, china clay, granite, coal and oil. They are used for building, as aggregate, for fuel and manufacturing uses.

Since the industrial revolution the scale of mining has increased dramatically to meet the needs of the growing manufacturing industries. Virtually all goods in everyday use have a component that originally came from the land through mining.

Finding mineral deposits in the past was based on chance, or on the experience of geologists who knew the likely places to look for rocks containing minerals. Most of these sources have now been found and exploited.

Above the atmosphere, the stratosphere and mesosphere are cooling faster than anybody thought. The heat trapped by the greenhouse gases in the lower troposhere causes the cooling. This is called radioative cooling and may be the "miner's canary" - the latest and largest sign that things are wrong. The cooling also creates more ice particles encouraging further ozone depletion.

New technologies are being employed to find other sources.. Satellites are now used to send back photographs of the earth's surface, showing features of the land in great detail.
Off the west coast of Mexico there are around 20 billion tonnes of the mineral phosphate, but because there are large reserves of phosphate on land, the sea bed deposits remain untouched.

All our minerals are finite resources so the future availability of them depends upon three factors:
  • Existing supplies.
  • The rate these supplies are being depleted.
  • New supplies being found.
It is this rate of extraction that makes them finite - not the minerals themselves.

Resources are rarely used up completely. What happens is the extraction becomes economically non-viable as it costs more to get less mineral out. It means that existing supplies are sometimes more than is first thought. Sometimes we know where there are mineral reserves, but it is not yet economical to extract them.

Rather than depend completely on new resources being found though, many people think that we should conserve existing stocks in order to extend the life of the supply. Conservation can include recycling more, finding substitutes for the mineral, or simply doing without it.
In west Devon there is a long-standing practice of redistributing mine wastes (containing as much as 10­30 000 mg Arsenic kg-1), without any controls, as landfill, soakaways and to cover domestic driveways. As a result, uncontaminated soils ­ and occasionally adjacent houses have become grossly contaminated

Building materials are extracted such as granite, sandstone and marble. These rocks are used throughout the world to construct buildings together with cement made from limestone. Small stones, gravel, mixed with sand, are known as aggregates and used in construction and road building.

Mineral extraction both from open-cast and deep mining have severe impacts on the environment. Mineral extraction from land usually has the following impacts:
  • Destruction of ecosystems and often human settlements
  • Subsidence and erosion of the land causing silting of lake sand streams
  • Waste and spoil heaps of contaminated land
  • Poisons entering water courses causing death and eventually entering coastal waters
  • Serious health problems



Land

Huge tracts of land are disfigured. Spoil and unusable rock from mining excavations is either piled up in spoil heaps, or used to infill other mining sites.

Both produce new landforms in the environment. In some areas, deep mining, especially for coal, has removed so much of the mineral that subsidence and landslides have occurred causing damage to buildings and loss of human life. Loss of vegetation causes erosion and further loss of land.

In addition to mineral extraction on land they can also be dredged from the sea-bed. There are estimated to be 500 billion tonnes of sand and gravel off the US Atlantic coast alone! In the U.K, a tenth of all the sand and gravel extracted is dredged from the ocean floor. Apart from destroying the ecosystems of the sea bed, it alters the way in which the tide and the currents move sand around the coastline.

This causes beaches to erode; protection against the sea is reduced; with the result that many areas of land, along with homes, are slowly being washed into the sea.

Salt is another mineral we get from the sea, and have done for 4,000 years. In the 1990's, an average 6 million tonnes per year are produced; part of the estimated 50,000 million tonnes of material removed from the earth's crust by mining every year.


Water

Extracting minerals also increases sediment loads in rivers, soil erosion and pollution of water courses on adjacent land. Quantities of sediment can alter the river's flow pattern and increase the risk of flooding. Mineral waste often contains poisonous that may pollute rivers and groundwater supplies, poisoning fish, plants, aquatic mammals and even drinking water.

Responsible mining companies pump mine waters that are polluted into 'tailings-dammed' ponds where the pollutants can be filtered out. These places are few. There is no obligatory legislation on most mining and mineral companies to carry this out.


Air

Another aspect of mining is the quantity of dust created in the atmosphere. This causes harm through suffocating plant life and ill health.


Health

Small dust particles can get into lungs where they can create scar tissue that makes breathing difficult. Silica based minerals are particularly dangerous causing the disease silicosis. Silica also contributes to the more widely known disease pneumoconiosis that causes suffering to many ex-miners.


Coal

This mineral is extracted worldwide, and so causes environmental impacts at a global level. Different extraction methods cause different environmental impacts.


Land

Opencast mining is the main method now used for the extraction of coal. The overburden is progressively removed before the coal is extracted, and then returned to the site as infill afterwards. This method is more popular now in the U.K, as shallow deposits can be removed in the most cost-effective way. Compared with deep mining however, it has a much greater environmental impact.

In America and Australia, a method called strip-mining is used. It is similar to opencast extraction, but the overburden and mineral waste are left exposed to the weather, with no restoration of the landscape.

Another mining method used for extracting coal, is deep or underground mining. This involves sinking shafts vertically into the earth, and then following the coal seams along narrow horizontal tunnels. In this method the rock has to be strong enough to allow underground cavities to remain after the coal has been removed.

Although coal requires little processing before being used, there is the problem of disposing of coal dust into tailings ponds. Although this is only a small percentage of the waste produced: 15 - 20%, out of a coal to waste ratio of 1:15, the very fine particles are easily blown away by the wind.

Between 1970 and 1980 in the U.K 67 million tonnes of waste from coal mining was produced annually: 61 million tonnes was disposed of in landfill, 3 million tonnes left underground and 3 million tonnes dumped at sea. PopUpFact

Although deep mining has a smaller environmental impact than underground mining, there is the problem of subsidence. This causes the collapse of the overlying strata, causing visual impact on the surface and severe disruption to local services such as drains, sewers and water and gas pipes.

In the United States, the Bureau of mines suggests that 32,000 square kilometres of land has been affected by subsidence, mainly due to coal extraction, and that by the year 2000, a further 10,000 square kilometres of land will have been affected.


Air

Dust is produced by drilling, blasting and while loading transport, releasing fine particles. 15-20 % of coal waste is dust.


Health

The fine dust (less than 10 microns) collects in the lungs of miners where it causes pneumoconiosis. Pneumoconiosis has debilitated the lives of thousands of miners.

The Pneumoconiosis etc (Workers' Compensation) Act 1979 covers a number of mineral diseases. In 1999, it was eventually recognised that coal dust causes a wide range of diseases. PopUpFact



Water

Coal mining in general, can cause water pollution. As rainfall passes through the waste tips, it leaches out chemicals which then run into streams, rivers or aquifers.

Oil

Oil is one of the most important mineral resources. It is mainly considered as an energy source. In the future we may consider it a waste to burn it. It is also a wonderful set of chemicals that can be used to make many raw materials for the production of synthetic polymers, including plastics and fibres.

The main impacts on the environment are to:
  • Decrease species diversity and productivity.
  • Damage marine wildlife.
  • Destroy marine and coastal habitats.
  • Decrease the scenic and economic value of the environment
  • Cause disease in humans through the consumption of contaminated seafood.



Land

All stages of the oil exploration and extraction process have an impact, and cause damage similar to other mining operations; visual disturbance, noise and dirt. Because offshore drilling rigs collect most oil, most of the environmental impacts remain unseen.


Water

Transporting the extracted oil around the world brings its own environmental impacts and hazards. One of the great concerns and problems is when the 'supertankers' that carry the crude oil are involved in accidents. PopUpFact

In 1967 the Torrey Canyon spilt 100,000 tonnes of oil off the coast of Britain; In 1979 the Amoco Cadiz, spilt 22,000 tonnes of oil off the coast of France; In 1989 the Exxon Valdez, spilt 36,000 tonnes of oil off the coast of Alaska.

These individual disasters are small when the total, routine discharges of oil from tankers before entering port, is estimated to be 1 million tonnes per year.

Health

Oil causes skin dermatitis and scrotal cancer among workers using oils all day. Some people become so "sensitised" that they only have to touch oil and they will break out in a rash all over.

© ep@w Publishing Company Ltd. 2000
2002 Edition