What Rocks Mean To Us

Rock Types And Formation


Just a point to note, is that the earth’s outer layer is mainly made up of rocks.Rock contains minerals ,and it’s chemical composition and make-up determines it’s main classification as: The Metamorphic Rocks, Igneous Rocks and Sedimentary Rocks.

Metamorphic Rocks

Metamorphic rocks are formed when the original rock composition is changed resulting into a different rock formation.This is mainly through excessive pressure and change in weather conditions especially heat.They are harder than their parent rocks and are not easily eroded.They include Gneiss,Marble,Graphite and Quartzite.

Igneous  Rocks

These Rocks form either on or below the earth’s surface.They are as a result of highly heated molten, solidified lava.They are divided into two groups: Plutonic and Volcanic.Plutonic rocks occur when molten lava cools and solidifies within the earth’s crust while that of the volcanic nature forms when lava solidifies on the surface of the earth. A good example of this is the pumice stone.

Sedimentary Rocks

These are  rock particles formed as a result of organic and chemical sediments formed through erosion and weathering .They are deposited by agents of denudation like wind and water,and accumulate to form sediments.

These are found on the earth’s surface and also in water bodies,where you are much more likely to find carbonate rocks, mud stone and sand stone .


They are classified as those that are:

Mechanically formed -Those formed through the deposition of particles which are derived from existing rocks, eventually laid down in layers (strata).

Organically formed -These are rocks formed from organic remains of either plants or animals.

Chemically formed -These are formed from mineral particles dissolved in water and solidified through precipitation of the same.


They are further sub - classified as:

Carbonates: Which are made up of carbonate compounds.

Sulphates: Containing sulphate compounds like gypsum which is a soft, white or colourless stone.

Chlorides: These are rock salts like table salt (sodium chloride).

Silicates: Formed from the deposition of silica.

Ironstone: Formed from various iron oxide deposits.


Economic  Value  of  Rocks

Various rocks contain valuable minerals like silver,zinc,copper,aluminium and lead.These are extracted and put into economic use, thereby earning revenue for countries.

Precious Stones are valuable to us. Diamond is a hard rock that is used in making jewelry and other accessories.

Sandstone, Limestone and Marble are used in the construction industry to make cement , gravel and sand aggregates.

Rock is a parent material for all soils.It is a determining factor in regards to the type of soil formed from it.

If you have ever wondered how water is easily stored on the earth’s surface where we can easily access it, the answer is right there: Rock.Non-porous and impervious ones are precious for this ability.

As an attraction,they are so unique and eye-catching like the breathtaking,natural forming volcanic rocks that grace our planet Earth.

Rocks Of Life

How Important They Are

Credit: morguefile