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About Minerals
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- Mineral is a naturally occurring organic and inorganic substance, having an orderly atomic structure and a definite chemical composition and physical properties.
- A mineral is composed of two or more elements. But, sometimes single element minerals like sulphur, copper, silver, gold, graphite etc. are found.
- These elements are in solid form in the outer layer of the earth and in hot and molten form in the interior.
- About 98 per cent of the total crust of the earth is composed of eight elements like oxygen, silicon, aluminium, iron, calcium, sodium, potassium and magnesium and the rest is constituted by titanium, hydrogen, phosphorous, manganese, sulphur, carbon, nickel and other
- The basic source of all minerals is the hot magma in the interior of the earth.
- When magma cools, crystals of minerals appear and a systematic series of minerals are formed in sequence to solidify so as to form rocks.
- Minerals such as coal, petroleum and natural gas are organic substances found in solid, liquid and gaseous forms respectively.
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Elements By Weight (%)
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- Oxygen 46.60
- Silicon 27.72
- Aluminium 8.13
- Iron 5.00
- Calcium 3.63
- Sodium 2.83
- Potassium 2.59
- Magnesium 2.09
- Others 1.41
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Some Major Minerals And Their Characteristics
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Feldspar
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- Silicon and oxygen are common elements in all types of feldspar and sodium, potassium, calcium, aluminium etc. are found in specific feldspar variety.
- Half of the earth’s crust is composed of feldspar.
- It has light cream to salmon pink colour.
- It is used in ceramics and glass making.
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Quartz
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- It is one of the most important components of sand and granite.
- It consists of silica.
- It is a hard mineral virtually insoluble in water.
- It is white or colourless and used in radio and radar.
- It is one of the most important components of granite.
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Pyroxene
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- Pyroxene consists of calcium, aluminum, magnesium, iron and silica.
- Pyroxene forms 10 per cent of the earth’s crust.
- It is commonly found in meteorites.
- It is in green or black colour.
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Amphibole
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- Aluminium, calcium, silica, iron, magnesium are the major elements of amphiboles.
- They form 7 per cent of the earth’s crust.
- It is in green or black colour and is used in asbestos industry.
- Hornblende is another form of amphiboles.
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Mica
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- It comprises of potassium, aluminium, magnesium, iron, silica etc.
- It forms 4 per cent of the earth’s crust.
- It is commonly found in igneous and metamorphic rocks.
- It is used in electrical instruments.
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Olivine
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- Magnesium, iron and silica are major elements of olivine.
- It is used in jewellery.
- It is usually a greenish crystal, often found in basaltic rocks.
- Besides these main minerals, other minerals like chlorite, calcite, magnetite, haematite, bauxite and barite are also present in some quantities in the rocks.
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Metallic Minerals
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These minerals contain metal content and can be sub-divided into three types:
- Precious metals: gold, silver, platinum etc.
- Ferrous metals: iron and other metals often mixed with iron to form various kinds of steel.
- Non-ferrous metals: include metals like copper, lead, zinc, tin, aluminium etc.
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Non-Metallic Minerals
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- These minerals do not contain metal content. Sulphur, phosphates and nitrates are examples of non-metallic minerals.
- Cement is a mixture of non-metallic minerals.
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