How many types of rocks do we have?

What is Rock?

A Rock is Natural Occurring, Solid Aggregate of minerals and a parent material of mineral soils. Rock is also combination of two or more minerals which has been fused together in a solid lump. Actually the natural process made them all together. Rocks are ordinarily found everywhere on Earth’s soil. They make up most forms of relief, as they often notice. For instance, rocks make up the mountains and most of the non-water portions of the earth’s surface. A rock is therefore defined as a solid natural mass of the consolidated mineral matter. This is because the rocks are formed by granules of different minerals that form large and hard masses.

rock hill


Rock formation is classified into rock types based upon characteristic relationship between the mineral grains.

rock types

 Igneous Rocks

Igneous rocks form the cooling of magma  molten materials in the earth’s crust. Eventually igneous means fire or heat. The molten materials are found beneath the earth’s crust and are usually subjected to extreme pressures and temperatures – up to 1200 ° C. Due to extreme levels of heat, igneous rocks contain no organic matter or fossils.

Sedimentary Rocks

 These rocks are already existed at earth’s surface. These are made up from the buildup of weathered and eroded preexisting rocks.  Every rock grain initially separated from other rocks. Small debris from rocky masses and eroded mountains along with soils, sand and other granite pieces are usually washed from the highlands to the lowlands. For example: Sedimentary rocks include argillaceous, limestone, sandstone and conglomerate.

Metamorphic Rocks

The name defines the formation whereby ‘meta’ means change and ‘morph’ means ‘form.’ Large tectonic movements and magma intrusions create earth movements and subsequently cause the rocks to move and shift. Metamorphic rocks form out of other rocks. They are primarily sedimentary or igneous rocks which have undergone changes as a result of extreme pressure and heat. Metamorphic rocks are formed by direct heating of magma and intrusions are called thermal or contact metamorphic rocks.

For Example: Marble and Slate

Rock Cycle

These rocks change over hundreds of years in six types of the rock cycle:

  • Weathering & Erosion:Igneous, sedimentary and metamorphic rocks on the surface of the earth are constantly being broken by wind and water.” Sand that carries the wind carries particles of rock as sandpaper. The water of the river and the breaking of the water comes off all rough edges of the rocks, leaving smooth stones of the river or pebbles behind.
  • Transportation: After Erosion the rock particles are washed away by wind or rain, streams, rivers and oceans.
  • Deposition: As rivers flow into the ocean, the current diminishes of rock particles (mixed with the soil) sink and becomes a layer of sediment.Often the sediment accumulates faster than it can be washed, creating small islands and forcing the river to break into many channels in a delta.
  • Compaction & Cementation: As the layers of sediment accumulate (above or below water), weight and pressure compact the bottom layers  The dissolved minerals fill the small voids between the particles and then solidify, acting as cement. After compaction and cementation, the sediment becomes sedimentary rock.
  • Metamorphism: For very long periods of time, the sedimentary and igneous rocks end in deep underground, due to the movement of the tectonic plates. While they go depth in earth, these rocks are exposed to heat and pressure which leads them into metamorphic rocks. That’s what happens in the depths of the earth.
  • Rock Melting: Can you imagine ‘rock hard’ rocks melting? That’s what they do in the depths of the earth! Metamorphic rocks underground melt to become magma,When a volcano erupts, magma flows out of it. (When magma is on the earth’s surface, it is called lava.) As the lava cools it hardens and becomes igneous rock.

Uses / Application of Rocks

Based on geology and mineralogy there are different types of rocks

  • Granite,limestone and sand stones are used for construction.
  • Slate is used for only roofs and floors
  • Some other solid stones are there which are used for making art statues.
  • Based upon the nature more or less suitable for different purposes.


There are variations in rock types

  • Due to some harmful minerals the rocks are lead to damage in stone when it is exposed to environment.
  • Knowledge is required for rock material in order to know how it would be used.
  • There are some limitations for various types of rocks.




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