How Do Igneous Rocks Form?

The word igneous means from heat or fire. Igneous rocks form through crystallization of magma or molten lava. There are two types of igneous rocks, extrusive igneous rocks and intrusive igneous rocks. Extrusive igneous rocks are formed when magma is crystallized on the surface of the earth, whereas intrusive igneous rocks are formed when magma gets crystallized deep in the crust of the earth.

Igneous rocks take the form of lava flows or ash and then they get crystallized. Intrusive rocks can be laccoliths, sills, dykes, and batholiths.

There are five types of igneous rocks categorized according to the mineral content found in each type. They are granite, diorite, gabbro, periodotite, and pegmatite. Granite contains mica, quartz, and feldspar. Diorite contains feldspar and another dark mineral with feldspar being dominant. Gabbro contains feldspar and another dark mineral with the dark mineral being dominant. Periodotite contains iron. Pegmatite contains large crystals of mica, quartz, and feldspar.

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