Our Earth is made mostly of rocks. The rocks are composed of mineral grains combined in different ways and having various properties.
- Minerals are naturally occurring chemical compounds in which atoms are arranged in three-dimensional patterns.
- The kind of elements and their arrangements lead to a particular appearance and certain properties for each mineral.
- The same chemical elements when arranged in different patterns show different characteristics.
- Classic examples are minerals made of the element carbon (C). Flat planes of carbon atoms form the mineral graphite, which is a gray, slippery, soft material. Carbon atoms arranged in a different pattern form the mineral diamond — the hardest natural substance known. Although they have the same chemical composition, their different internal crystal structures form very different materials.
- A mineral is composed of two or more elements. But, sometimes single element minerals like sulphur, copper, silver, gold, graphite, etc are also found.
- The basic source of all minerals is the hot magma in the interior of the earth.
- When magma cools, crystals of the minerals appear and a systematic series of minerals are formed in sequence to solidify so as to form rocks.
- The minerals which contain metals are called as metallic minerals (eg: Haematite) and the metallic minerals which are profitably mined are called as the ores.
- The crust of the earth is made up of more than 2000 minerals, but out of these, only six are the most abundant and contribute the maximum.
- These six most abundant minerals are feldspar, quartz, pyroxenes, amphiboles, mica and olivine.
Some Major Minerals:
Quartz:
- It is one of the most important components of sand and granite.
- It consists of silica and it is a hard mineral virtually insoluble in water.
- It is usually white or colourless.
- They are used in the manufacturing of radio, radar, etc.
Feldspar:
- Silicon and oxygen are major elements of all types of feldspar.
- Sodium, potassium, calcium, aluminium, etc are found in specific feldspar varieties.
- Half of the earth’s crust is composed of feldspar (plagioclase (39%) and alkali feldspar (12%)).
- It has light cream to salmon pink colour.
- It is commonly used in ceramics and glass making.
Pyroxene:
- The common elements in pyroxene are Calcium, aluminium, magnesium, iron and silicon.
- About 10% of the earth’s crust is made up of pyroxene.
- It is commonly found in meteorites.
- Its colour is usually green or black.
Amphibole:
- Aluminium, calcium, silicon, iron and magnesium are the major elements of amphiboles.
- They form 7% of the earth’s crust.
- It is green or black in colour and is used in asbestos industries commonly.
- Hornblende is another form of amphiboles.
Mica:
- It is made up of elements like potassium, aluminium, magnesium, iron, silicon, etc.
- It forms 4% of the earth’s crust.
- It is commonly found in igneous and metamorphic rocks.
- Mica is widely used in electronic instruments.
