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World Mineral Resources
Minerals include all materials extracted from the earth. Minerals include
- (a) metallic minerals such as iron, copper, aluminium, lead, zinc, tin and others
- (b) mineral fuels like coal, lignite, petroleum and natural gas
- (c) non-metallic minerals like limestone, gypsum, sandstone, sand, clay and other materials.
Exploitation of mineral resources is essential. Iron and Steel is needed for the manufacture of machinery, locomotives, automobiles, ships and other equipment. Copper and aluminium are essential for transmission of electricity. Limestone is used for manufacture of cement. There is no economic activity, which can be performed without the use of mineral products. Developed nations consume large quantities of fuels and other minerals. The quantity of steel consumed per capita is often taken as a measure of economic development of a nation.
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The extraction of mineral resources from the earth is called the 'robber industry' as the available stock will get exhausted after some time. The stock of minerals available in an area cannot be increased by human effort. It is not also possible to replace the minerals once mined. The existing minerals have accumulated over millions of years of past geological periods. Therefore natural replacement of minerals is an extremely slow-process depending on earth movements. Their availability may be increased by discovery of new deposits or development of a new technology for mining low-grade ores.
Modes of occurrence and methods of mining - Minerals normally occur in nature as ores containing a number of substances. Mineral ores are mined when many conditions are favorable. Ores, which are of high grade, are taken up for mining in the first instance. In the case of metallic ores, the metal content in the ore is the main criterion. The size of the deposit is another factor to be considered for taking up the ore for mining.
The mode of occurrence of ore is an important factor. Certain minerals like iron ore or bauxite occur on the surface. They are mined by quarrying method. When mineral ores occur at shallow depth usually less than 60 meters, open cast mining is applied. More commonly ores occur at great depths as beds or seams between other rocks or as lobes or veins. Coal occurs as thick seams or layers; copper, lead, zinc, gold and silver ores are found in the form of lobes or veins. Such minerals are mined by underground mining or shaft mining method. Vertical shafts and horizontal or inclined tunnels are cut to reach the place of mining.
Some minerals like tin or gold occur in alluvial deposits in riverbeds. The ores have been eroded from their original sites by river action and deposited on the valley floor. These deposits are called placer deposits and the mineral is recovered by placer mining. This consists of washing the ores by large quantities of water and separating the heavier ore particles from lighter materials by panning. Larger deposits are worked by dredgers.
The cost of mining the ores is an important factor for selecting the ores to be developed. Underground mining is more expensive than quarrying, open cast mining or placer mining. Minerals of high value such as gold or uranium can be mined at high cost because they fetch high prices. Normally ores, which can be worked cheaply, are developed first.
The location of the ore deposit, its accessibility by road or rail and the climatic conditions of the area also influence its development. Gold mining in Western Australia is being undertaken in an unfavorable environment of tropical desert. The availability of labour, the fluctuations in demand for the mineral, changing international prices, transport costs to markets are other factors which affect mining of minerals.
More commonly mineral ores from different mines are collected at a central point where the smelter may be set up for refining the ore. Availability of skilled labour, adequate power and transport facilities to marketing centres is factors to be considered in locating the place of refining. The cost of refining should be taken into account in mining the ore.
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