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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. |
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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. |
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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. |
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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
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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.
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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. |
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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.
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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. |
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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.
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