Rocks and Minerals

Rocks and Minerals

This article deals with ‘Rocks and Minerals.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here


  • Naturally occurring organic and inorganic substance, having an orderly atomic structure and a definite chemical composition and physical properties.
  • Composed of two or more elements. But, sometimes single element minerals like sulphur, silver, gold, graphite etc. are found
  • Magma is the source of almost all minerals.

Types of Minerals

a. Metallic Minerals

These minerals contain metals and can be sub-divided into

Precious Metals gold, silver, platinum
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.

b. Non-Metallic Minerals

  • 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.


  • A rock is an aggregate of one or more minerals.
  • Rocks do not have definite composition of mineral constituents.
  • Petrology is the science of rocks.
  • The age of the rock is determined based on Carbon-14 dating.

Type of rocks

a. Igneous Rocks

  • Igneous rocks (Ignis in Latin means ‘Fire’) are formed when magma cools and solidifies.
  • They  are known as primary rocks
  • Igneous rocks are classified based on texture. 
    1. If cooled slowly at great depths : Large grains  
    2. Sudden cooling (at the surface) :  small grains.
    3. Intermediate  cooling : intermediate size of grains .
  • Granite, gabbro, pegmatite, basalt, volcanic breccia and tuff are some of the examples of igneous rocks.

b. Sedimentary Rocks

  • Formed by lithification of sediments
  • They are also known as detrital rocks
  • Examples : sandstoneshale, loess , chalk, coal , limestone etc

c. Metamorphic Rocks

  • Metamorphic rocks are formed when already consolidated rocks undergo reorganization in structure due to excessive pressure (through the process called Metamorphism)
  • Eg : Gneiss, syenite, slate, schist, marble, quartzite, anthracite, diamond  etc.

Igneous  and metamorphic rocks together account for 95 percent of the earth while rest 5% are sedimentary rocks.

Rock Cycle

Rocks do not remain in their original form for long but may undergo transformation.  Rock cycle is a continuous process through which old rocks are transformed into new ones.

Rock Cycle

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