Rocks

Rock is the solid mineral material that forms part of the surface of the earth, exposed on the Earth’s surface or underlying the soil.
Rock is divided into following three types:
1. Igneous Rocks
2. Sedimentary Rock
3. Metamorphic Rock

Igneous Rock is normally formed by the solidification of the molten magma.
All other types of rocks are formed by the igneous rock; therefore, igneous rock is also known as primary rock.
About 95% of the Earth’s crust is made of igneous rock.
Granite, Basalt, and Volcanic rock are the major types of igneous rock.

The rocks, which is formed because of the deposition of weathered remains of igneous rocks, is known as ‘Sedimentary Rock.’
Sedimentary rocks share 5% of the Earth’s surface, but cover (in terms of area) about 75% of Earth’s (exposed) surface.
Sedimentary rocks also contain organic materials (i.e. source of energy for the human beings).
Major examples of sedimentary rocks are Gypsum, Limestone, Chalk, Coal, Conglomerates, Sandstone, Claystone, etc.

Because of the intense pressure, high fluctuating temperature, and presence and absence of moisture and chemicals, over a period of time, igneous rock or sedimentary rocks get modified (metamorphosed) and called as ‘Metamorphic Rock.’
Major examples of metamorphic rock are Slate, Gneiss, Marble, Quartzite, etc.