Rock and Rock Cycle

What Are Rocks?
Rocks are mineral aggregates with a combination of properties of all the mineral traces. Any unique
combination of chemical composition, mineralogy, grain size, texture, or other distinguishing
characteristics can describe rock types. Additionally, different classification systems exist for each
major type of rock. There are different types of rocks existing in nature.
Rocks which are found in nature rarely show such simple characteristics and usually exhibit some
variation in the set of properties as the measurement scale changes.
Types of Rocks
There are three types of rocks:
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
Igneous Rock
Igneous rock is one of the three main rock types. Igneous rock is formed through the cooling and
solidification of magma or lava. Igneous rock may form with or without crystallisation, either below
the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.
Igneous rock
This magma can be derived from partial melts of existing rocks in either a planet’s mantle or crust.
Typically, the melting is caused by one or more of three processes: an increase in temperature, a
decrease in pressure, or a change in composition.
Types of Igneous Rock
Following are the two types of igneous rock:

Intrusive igneous rock: These rocks crystallise below the earth’s surface resulting in large crystals as
the cooling takes place slowly. Diorite, granite, and pegmatite are examples of intrusive igneous
rocks.
Extrusive igneous rock: These rocks erupt onto the surface resulting in small crystals as the cooling
takes place quickly. The cooling rate for a few rocks is so quick that they form an amorphous glass.
Basalt, tuff, and pumice are examples of extrusive igneous rock.
Igneous Rock Examples
Basalt Diorite
Granite Mica and quartz
Sedimentary Rock
The sedimentary rocks are formed by the deposition and subsequent cementation of that material
within bodies of water and at the surface of the earth. The process that causes various organic
materials and minerals to settle in a place is termed sedimentation.
Sedimentary Rock
The particles that form a sedimentary rock by accumulating are called sediment. Before being
deposited, the sediment was formed by weathering and erosion from the source area and then
transported to the place of deposition by water, wind, ice, mass movement or glaciers, which are
called agents of denudation. Sedimentation may also occur as minerals precipitate from water
solution or shells of aquatic creatures settle out of suspension.
Types of Sedimentary Rock
Following are the three types of sedimentary rock:
Clastic sedimentary rocks: These rocks are formed from the mechanical weathering debris.
Sandstone, and siltstone are examples of clastic sedimentary rocks.
Chemical sedimentary rocks: These rocks are formed from the dissolved materials that precipitate
from the solution. Iron ore and limestones are examples of chemical sedimentary rocks.
Organic sedimentary rocks: These rocks are formed from the accumulation of plant and animal
debris. Coal, and some dolomites are examples of organic sedimentary rocks.
Sedimentary Rock Examples
Halite Limestone
Sandstone Siltstone
Metamorphic Rocks
The metamorphic rocks make up a large part of the Earth’s crust and are classified by texture and by
chemical and mineral assemblage. They may be formed simply by being deep beneath the Earth’s
surface, subjected to high temperatures and the great pressure of the rock layers above it.
Metamorphic Rocks
Metamorphic rocks arise from the transformation of existing rock types, in a process called
metamorphism, which means “change in form”. The original rock is subjected to heat with
temperatures greater than 150 to 200°C and pressure around 1500 bars, causing profound physical
and/or chemical change.
Types of Metamorphic Rock
Following are the two types of metamorphic rock:
Foliated metamorphic rocks: These rocks are produced by exposure to heat and pressure which
makes them appear layered. Phyllite and gneiss are examples of foliated metamorphic rocks.
Non-foliated metamorphic rocks: These rocks don’t have layers. Marble and quartzite are examples
of non-foliated metamorphic rocks.
Metamorphic Rock Examples
Marble Quartzite
Slate Phyllite
Frequently Asked Questions – FAQs

Q1
What are rocks?
Rocks are mineral aggregates with a combination of properties of all the mineral traces. Any unique
combination of chemical composition, mineralogy, grain size, texture, or other distinguishing
characteristics can describe the type of rock.
Q2
What are the different types of rocks?
There are three types of rocks:
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
Q3
Which is the most common type of igneous rock?
Basalt is the most common type of igneous rock. The majority of the ocean floor is composed of
basalt.
Q4
Give some examples of sedimentary rocks.
Some common sedimentary rocks are:
Limestone
Chalk
Clay
Sandstone
Shale
Q5
How are sedimentary rocks formed?
Sedimentary rocks are formed by the deposition and subsequent cementation on the material at the
Earth’s surface within the bodies of water. These rocks are formed in four ways:
Deposition of weathered remains of other rocks
Accumulation and the consolidation of sediments

Deposition of the results of biogenic activity
Precipitation from solution.

Rock and Rock Cycle

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Rock and Rock Cycle

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What Are Rocks?

There are three types of rocks:

Types of Igneous Rock

Following are the two types of igneous rock:

Igneous Rock Examples

Granite Mica and quartz

Types of Sedimentary Rock

Following are the three types of sedimentary rock:

Sedimentary Rock Examples

Types of Metamorphic Rock

Following are the two types of metamorphic rock:

Metamorphic Rock Examples

Frequently Asked Questions – FAQs

What are rocks?

What are the different types of rocks?

There are three types of rocks:

Which is the most common type of igneous rock?

Give some examples of sedimentary rocks.

Some common sedimentary rocks are:

How are sedimentary rocks formed?

Deposition of weathered remains of other rocks

Accumulation and the consolidation of sediments

Precipitation from solution.

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