Intrusive vs. Extrusive Igneous Rocks: 6 Different Examples

Igneous Rocks
© vvoe/

Written by Gail Baker Nelson

Updated: July 6, 2023

Share on:


Of the thousands of rocks and gems worldwide, some are classified as igneous rocks. To understand what they are, the easiest thing to think of is that they were born in fire — and the word igneous comes from the Latin word ignis, which means fire.

They’re generally grouped into one of two types. One kind forms underground from magma that cools slowly. The other formed from lava that cooled rapidly after being ejected from a fissure in the ground.

Extrusive Igneous Rocks

Pumice - Types of Igneous Rocks

Pumice is one of many examples of extrusive igneous rocks, which form rapidly after a

volcanic eruption



These are the rocks you find after a volcano has erupted. Whether it was the result of a pyroclastic flow like Pompei or a volcanic fountain like those in Hawai’i, the lava they produce results in rocks. They can be any number of types, but the common thread is that they all form rapidly after an eruption.

This type of igneous rock is also called volcanic because it came from a volcano. Interestingly, the lava that formed some of these rocks has an intrusive counterpart. 

Intrusive Igneous Rocks 

Plutonic Bodies Vector - Types of Igneous Rocks

This demonstrates where extrusive igneous rocks form compared to intrusive igneous rocks.


This type of rock forms below the Earth’s surface. They develop from magma that’s forced into pockets around older rocks, allowing them to cool slowly.

Unlike lava, which cools within days or hours of being ejected, magma takes millions of years to cool. As a result, it results in varying sizes of crystal growth, giving the rocks a grainy texture. Most often, intrusive igneous rocks are medium- to coarse-grained, and some mineral composition is visible to the naked eye. 

Some geodes are intrusive igneous rocks!

What Kinds of Rocks Are Igneous?

There’s a wide variety of igneous rocks; some are polished up and used as gemstones. Basalt, obsidian, and granite are a few that come to mind! Here are a few of our favorite igneous rocks.


Rhyolite - Types of Igneous Rocks

The high silica content in rhyolite, an extrusive igneous rock, means the magma that formed it was thick and viscous.

©Yes058 Montree Nanta/

Of all the volcanic rocks, rhyolite has the most silica. Its high silica content makes the magma that forms rhyolite thick and viscous, making it more likely to be violently expelled from the Earth.

This extrusive igneous rock cools quickly and is 20% to 60% quartz, and the rest consists mainly of alkali feldspar. Rhyolite is usually lighter-colored and either fine-grained or glassy.


Peridotite - Types of Igneous Rocks

Peridotite is a general term for several rocks, all of which are intrusive.


Compared to other igneous rocks, peridotite is relatively low in silica. Peridotite is a generic term that encompasses quite a few different rocks — all are intrusive igneous rocks. 

It often contains chromite, which is where we get chromium. Peridotite is coarse-grained and dark-colored. Olivine is usually the primary mineral in peridotites, and they don’t have very much quartz or feldspar in their makeup.



Obsidian is generally an extrusive igneous rock, usually forming along the edges of a volcanic dome.


Volcanic glass.

You’ll often hear obsidian called this, and it’s not wrong! It’s usually an extrusive igneous rock that forms on the Earth’s surface. You’ll typically find it along the edges of a volcanic dome, lava flow, where lava runs into the water, and when lava cools while it’s still airborne. 

However, it can also form an intrusive rock. You can sometimes find obsidian around the edges of a sill or a dike. Interestingly, the magma that produces obsidian also produces granites and rhyolites, and they’re often located near one another. 

Obsidian is usually black, but brown, tan, or green are relatively common. In rare cases, obsidian can also be blue, red, orange, or yellow. Because it’s glass, it’s not stable. Over time, it begins to crystallize, giving you snowflake obsidian.


Scoria - Types of Igneous Rocks

Scoria looks similar to pumice, and like pumice, is extrusive.


The next rock on our list is extrusive and looks a lot like pumice, and if you didn’t know better, you might think it was pumice. However, scoria is almost always black, dark gray, or reddish brown, but pumice is much lighter-colored. It forms from basaltic magma that is full of dissolved gasses. Scoria’s bubbly nature is the result of all those gasses being released when the magma escapes from the volcano. 

The magma that forms scoria is under tremendous pressure. As a result, some of it has large amounts of dissolved gasses released when it leaves the magma chamber. As a result, the magma becomes foamy and frothy; as it cools, the bubble pockets stay and create scoria. 

Scoria is popular as a construction material and reduces the overall weight of concrete. Its other uses include sauna rocks, landscaping ground cover, and hydroponic gardening substrate. 

Diabase (Also Known as Dolerite)

Diabase (Dolerite) - Types of Igneous Rocks

Stonehenge was cut from diabase or dolerite. It is an intrusive igneous rock.


You can see our next rock in Stonehenge – the people who built Stonehenge cut the stones from diabase! It’s a highly durable rock that’s also beautiful when polished.

Diabase, which in the U.K. is also called dolerite, is an intrusive igneous rock that forms relatively close to the surface. It cools pretty slowly in shallow intrusions like sills and dikes.

According to, this rock’s composition figures heavily with labradorite, which can be up to 70% of the total mineral content. Diabase is often crushed and used as aggregate for concrete, asphalt, unpaved roads, and a filter stone for drainage. 


Grainte Rock - Types of Igneous Rocks

Granite forms deep underground, making it an intrusive igneous rock.


We use granite in everything from countertops to building façades. It forms deep underground as an intrusive igneous rock. Granite’s composition includes quartz, feldspar, mica, and other minerals. The minerals can give the rock different colors, like red, pink, white, or gray. In addition, it’s coarse-grained with dark minerals visible — it makes granite look speckled and gives the rock its distinctive appearance.

Granite is visible worldwide. Yosemite’s Half Dome is granite, and Mount Rushmore in South Dakota.

Other Igneous Rocks

The few we listed here aren’t the only igneous rocks; there are dozens! Although they all fall into the two categories of extrusive and intrusive, they all have different properties, mineral compositions, and textures. In addition, many form different types of rocks depending on how or where they cooled. For example, gabbro, basalt, and diabase have similar compositions but form at different locations. 

We use some in construction, but some aren’t used at all. A few, like kimberlite, are known to hold diamonds and other precious stones.

This great big blue marble we call home always seems to surprise us.

Share this post on:
About the Author

Gail Baker Nelson is a writer at A-Z Animals where she focuses on reptiles and dogs. Gail has been writing for over a decade and uses her experience training her dogs and keeping toads, lizards, and snakes in her work. A resident of Texas, Gail loves working with her three dogs and caring for her cat, and pet ball python.

Thank you for reading! Have some feedback for us? Contact the AZ Animals editorial team.