Rocks and their types

 In this article we are going to learn about rocks and their types. How rocks are formed and what are their most important and famous types, we'll discuss in this topic Let's start.

Rocks:

Rocks are made up of different types of minerals. Minerals are naturally occurring solid organic material that constitutes rocks. 

Types of rocks:

Rocks are of three types:

• Igneous rocks 
• Sedimentary rocks 
• Metamorphic rocks

Here's a little table to understand basics of these rocks:

Characteristics	Igneous rocks	Sedimentary rocks	Metamorphic rocks
Formation	Formed by cooling of lava	By the cementation and calcification of rocks pieces	Formed under immense heat and pressure
Types	Two types: Extrusive Intrusive	Three types: Clastic Bioclastic/Organic  Crystalline	Two types: Foliated  Non foliated
Example	Granite, Basalt	Rock salt, limestone, sandstone	Marble,

Let's look at these rock types in detail:

Igneous rocks: They are formed by the cooling and solidification of lava. 

Types of igneous rocks:

Igneous rocks are of two types on the basis of the their constituents and place of formation.

• Intrusive igneous rocks 
• Extrusive igneous rocks 

Intrusive rocks:  

• These rocks are formed under the earth with magma. 
• These rocks have large crystal particles because they cool down slowly as the temperature under the earth is warmer. 
• So, it take a long time to cool and form larger crystal particles that are visible to naked eye.

Extrusive rocks: 

• These rocks are formed outside the earth with lava and they have smaller or no crystal particles. 
• The reason behind not having crystal particles or very much smaller crystal that are not visible to naked eye is the instant cooling of the lava as it is exposed to a cooler temperature than the hotter temperature inside the earth. 
• The insTant cooling of lava leaves air bubbles in these rocks.  

Fast review: The part of a volcano which 

is outside the earth is lava, and magma is inside the earth.

Sedimentary rocks: formed by the compaction and cementation of rocks pieces that are separated from other larger rocks. There are three types of sedimentary rocks on the basis of crystal type and formation.

• Clastic: The shape of crystal determine the quality of rocks. The crystals of these can be round, angular, fine or any other shape.

• Crystalline rocks: Those rocks that are formed by evaporation and precipitation in water. Once a rock is mixed in water, the water evaporates and the crystals are seen.

• Bioclastic/organic: They are formed of remains of plants/ or living things.

Metamorphic rocks: Rocks that are formed by the intense heat and pressure, as the pressure increases the rocks formed have layers. The very important and crucial feature too recognize is layers present on the rocks. There are two types of metamorphic rocks.

• Foliated.
• Non-foliated

Foliated metamorphic rocks: The foliated metamorphic rocks have two types on the basis of mineral alignment.

• Mineral Alignment foliated
• Banding foliated

Mineral alignment:  The minerals line up in these rocks due to intense pressure .

Banding: This is the intense form of mineral alignment and the mineral line up in light and dark bands in result of even more intense pressure.

Non foliated metamorphic rocks: These rocks are formed by either intense pressure under the earth or intense heat when they come in contact with magma.

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