Minerals and rocks Upsc

Minerals and rocks

The earth is made of different kinds of elements and these elements are in solid form in the outer layer and hot and molten form in the interior of the earth.

Around 98% of the total crust of the earth is composed of eight elements:

  1. Oxygen – 46.6%,
  2. Silicon- 27.72%,
  3. Aluminium – 8.13
  4. Iron – 5%
  5. Calcium – 3.63%
  6. Sodium – 2.83%
  7. Potassium – 2.59%
  8. Magnesium – 2.09%

Others – 1.41% (Titanium, Hydrogen, Phosphorous, manganese, sulphur, carbon, nickel, etc). There are at least 2000 minerals are identified in the earth’s crust.

But only six major mineral groups are known as Major rock-forming minerals. The rocks are made up of different minerals.

What is Mineral?

The mineral is a naturally occurring substance that is both organic and inorganic in nature.

These substances have an orderly atomic structure and definite chemical and physical properties. Minerals are composed of two or more elements and are also found single such as sulphur, gold, graphite, silver, copper, etc.

Basic Source of Minerals

The basic source of all minerals is the hot magma found in the interior of the earth.

The rocks are formed after the magma cools and then crystals of minerals appear and a systematic series of minerals appear and a systematic series of the mineral are formed.

Fossil fuels such as coal, petroleum, and natural gas are minerals that are organ substances found in Solid, Liquid, and gaseous forms respectively.

Metallic Minerals

Precious Metals – Gold, silver, Platinum, etc

Ferrous Metals – Iron, and other metals mixed with iron to form different kinds of steel.

Non-Ferrous Metals – Metals such as copper, zinc, lead, etc are called Non-Ferrous metals.

Non-Metallic Minerals

The minerals which do not contain metal are called Non-Metallic Minerals.

Example: Sulphur, Phosphates, nitrates, etc.

Cement is made up Non-Metallic Minerals.

Characteristics of Major Minerals


Silicon and oxygen are common elements in all types of feldspar and sodium. Potassium, calcium, aluminium, etc are found in specific feldspar varieties.

Almost half of the earth’s crust is composed of feldspar. Feldspar has a light cream to salmon pink color and it is used in ceramics and glassmaking.


Quartz 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.

Quartz is white or colorless and it is used in Radar and radio, and also it is one of the most important components of granite.


Pyroxene consists of calcium, aluminium, magnesium, iron, and silica. Pyroxene forms 10% of the earth’s crust and is commonly found in meteorites. Its color is green or black.


Aluminium, calcium, silica, iron, magnesium are the main elements of amphiboles. Amphibole forms 7% of the earth’s crust and it is green or black in color and used in the Asbestos industry.

Hornblende is another form of amphiboles.


Mica comprises potassium, aluminium, magnesium, iron, silica, etc. Mica forms 4% of the earth’s crust and it is commonly found in igneous and metamorphic rocks.

It is used in electrical instruments.


Magnesium, iron, and silicon are major elements of olivine. Olivine is used in jewelry and it is usually a greenish crystal, which is often found in basaltic rocks.

Other important minerals are Chlorite, calcite, magnetite, haematite, bauxite, barite, etc.


* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.