Igneous Rocks
Chapter 2.3
Igneous Rock is any rock formed from
magma or lava.
 The name Igneous comes from the Latin
word ignis, meaning “fire.”
 Igneous rock is classified according to
their origin, texture, and mineral
composition.

Igneous Rock
Extrusive rock is igneous rock formed
from lava that erupted onto Earth’s
surface.
 Basalt is the most common extrusive
rock.
 Basalt is one of the most common rocks
on Earth.
 A layer of basalt forms much of Earth’s
ocean floors.

Origin…
Intrusive rock formed when magma
hardened beneath Earth’s surface.
 The most abundant intrusive rock is
granite.
 Granite forms the core of many mountain
ranges.

Intrusive Rock
The texture of igneous rock depends on
the size and shape of its mineral crystals.
 Igneous rock can have very different
textures.
 Porphyry is an intrusive rock. It looks like
Jello with fruit inside.
 Obsidian is an extrusive rock. It is like a
smooth, shiny piece of glass.

Texture
Most of Earth’s minerals contain silica, a
material formed from oxygen and silicone.
 Lava is low in silica and usually produces
dark colored rock.
 Magma is high in silica and usually
produces light colored rock.

Mineral Composition…

Many igneous rocks are hard, dense, and
durable.

People throughout time have used
igneous rock for tools and building
materials.

The rough surface of pumice is known to
be used for polishing and cleaning.
Uses of igneous rock…