Igneous Rock

Chapter 4 Section 2

Igneous rocks

Igneous rocks are classified by their origin, texture, and mineral composition

Origin and Texture

• Extrusive rock- rock that forms from lava on or near Earth’s surface

- they have small crystals and

fine-grained texture due to quick

cooling

Andesite

Origin and Texture

- Some cool so fast that no crystals

form and rock has a glassy texture

Obsidian

Origin and Texture

• Intrusive rock – rock that forms from magma beneath Earth’s surface

- they have large crystals and a coarse-

grained texture due to slow cooling

Granite

Mineral Composition

• Minerals low in silica are dark colored and dense

• Minerals high in silica are usually light colored and less dense

Uses of Igneous Rock

Statues

Fortresses

Bridges

Uses of Igneous Rock

CountertopsGravel

StreetsCleaning, polishing, andcutting tools