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Rocks and Minerals

You probably see rocks and even minerals almost every day. But what do you really know about them? Do you know how many minerals there are on planet Earth?


Did you know that there are three types of rocks, and they are all formed in different ways by nature?

Do you know some of the really cool ways rocks have helped people throughout history? Keep reading to find out!

What is a mineral?

All minerals are solid, naturally forming, and have their own unique chemical composition. This is what makes each mineral special and different from other minerals.

Minerals also have a crystalline structure, meaning their atoms are arranged in specific shapes and patterns.


Think you don’t know any minerals? You probably do, actually. Some common minerals are gold, silver, diamond, and copper. But that’s not all. There are over 4000 minerals on the planet!

What is a rock?

Just like minerals, rocks are solid and naturally forming. In fact, all rocks are made from two or more minerals. There are three different types of rocks, and all three form in different ways.

3 Different Types of Rock: Igneous rocks, Sedimentary rocks, and Metamorphic rocks

Igneous rocks

Igneous rocks are created when magma cools and hardens. Magma is the same material that forms lava (that really hot stuff that explodes out of volcanoes).

There are two types of igneous rock: extrusive igneous rock and intrusive igneous rock, and the type depends on where the rock was formed.

If the rock is formed by cooled, hardened magma on the surface of the Earth, it is called extrusive igneous rock.


Because volcanoes help form extrusive igneous rocks, they are sometimes called volcanic rocks. These rocks form very fast and usually look glassy or shiny. Some examples are basalt, obsidian, and pumice.

As you might have guessed from the name, intrusive igneous rock forms inside of the Earth, below its surface.

When magma cools and hardens beneath the surface, it is a much longer process, so intrusive igneous rocks are usually grainy and rough.

Granite and gabbro are examples of intrusive igneous rock.

Scientists have identified over 700 varieties of igneous rock. That’s a lot of rocks, and we still have two types left to learn about!

Sedimentary rocks

Sedimentary rocks form from the build-up of materials like the remains of plants or animals, minerals, and eroded fragments (pieces) of other rocks. Fossils are most often found in sedimentary rocks.

Sedimentary rocks are often found at the bottom of lakes or oceans. These rocks form in layers called strata, which can sometimes be seen on the side of cliffs.

Examples of sedimentary rocks are chalk, coal, and sandstone.

Metamorphic rock

Metamorphic rocks start out as igneous or sedimentary rocks, but then they are transformed by extreme pressure or heat.

They can be formed from tectonic plates (pieces of the Earth’s crust) colliding and creating friction, from pressure under Earth’s surface, or from really hot magma.

Marble is a type of metamorphic rock that started out as a sedimentary rock called sandstone. Another type of metamorphic rock is gneiss, which often begins as the igneous rock granite.

Why are rocks and minerals important?

For millions of years, rocks and minerals have been very useful to humans.

Throughout history, rocks like jade were used to make tools and weapons like knives, hammers, axes, and hooks for catching fish.

Before humans had matches, rocks were used to create different tools meant for starting fires.


Minerals and rocks are found in batteries, soap, paper, detergent, toothpaste, makeup, sports equipment, and more.

Rocks are used in all kinds of construction like ships, cars, planes, buildings, and appliances. Some types of rocks like granite are used to make statues, countertops, and gravestones.

Imagine if we didn’t have any of the products listed above. Wow! Where would we be without rocks and minerals?

ship building

Facts about rocks and minerals

Of the over 4000 minerals on planet Earth, only about 30 of them can be commonly found in Earth’s crust.

There are seven different physical properties or characteristics used to identify and label minerals: crystal form, hardness, fracture or cleavage, luster, color, streak, and density.


95% of the Earth’s crust is made of igneous rock.

It is estimated that the average person on the planet Earth will use over one million pounds of rocks, minerals, and metals in a lifetime.

The biggest nugget of pure gold was found in Australia in 1869. It weighed 156 pounds, as much as an adult human!

gold bars


Next time you see a rock or mineral, think about all of these fascinating facts. Rocks are a lot more interesting than you thought!

Earth Science

layers of the earth cartoon