How Do We Classify Igneous Rocks?

Igneous rocks can be divided into four categories based on their chemical composition: felsic, intermediate, mafic, and ultramafic.

How Do We Classify Igneous Rocks?

Igneous rocks are one of the three main types of rocks found on Earth. They form when molten rock, or magma, cools and hardens. Igneous rocks are classified based on two main criteria: the composition of the rock and the texture of the rock.

Composition of Igneous Rocks

There are two main categories of igneous rocks based on composition: intrusive and extrusive. Intrusive igneous rocks form when magma cools slowly beneath the Earth’s surface, allowing the minerals to crystallize slowly. Examples of intrusive igneous rocks include granite and gabbro. Extrusive igneous rocks form when magma reaches the Earth’s surface and cools quickly. Examples of extrusive igneous rocks include basalt and andesite.

Texture of Igneous Rocks

Igneous rocks are also classified based on texture, which is a measure of the size and shape of the crystals that form when the magma cools. Texture is further divided into two categories: phaneritic and aphanitic. Phaneritic igneous rocks form when magma cools slowly beneath the Earth’s surface. These rocks contain large, easily visible