5 minute read
Minerals and Rocks
Amazing Fact!
Diamond is a mineral. It is the hardest natural substance on Earth. The only other thing that can scratch a diamond is another diamond!
What Are Minerals?
Minerals are non-living substances that are formed naturally in the Earth. They are usually found underground, in rocks and soil. Minerals are also found underwater in rivers, lakes and the ocean.
Minerals are made of chemicals. They do not come from the remains of living things. You are already familiar with many types of minerals. Metals, such as gold, silver, iron and copper are minerals. Quartz, salt and talc are minerals too.
quartz
Himalayan rock salt
gold
What Are Rocks?
Rocks are naturally occurring non-living things found on and under the Earth’s surface. All rocks are made up of one or more minerals.
Rocks can be found all over the Earth’s surface. They can be found on mountains and hills, in fields and valleys and along rivers and streams. Rocks line our coastlines and can be found underwater too.
In what ways are rocks similar to each other? How can rocks be different?
AB Activity 8.1 Amazing Fact!
The largest single rock formation in the world is Uluru in central Australia. The gigantic rock reaches a height of over 850 meters above ground and another 2.5 kilometers below ground!
Properties of Rocks
Rocks are made up of tiny mineral particles called grains. Rocks can have different properties such as color, texture and arrangement of the grains that form them. These rocks are different in color.
These rocks are different in texture.
Try This!
In small groups, go into your schoolyard and collect small rocks. Discuss the properties of the rocks. Classify the rocks in two different ways.
rough rocks smooth pebbles
These rocks have grains of different sizes.
The grains in these rocks are arranged in different ways.
What are some properties of the rocks in your schoolyard?
AB Activity 8.2
Go Online!
Learn about different types of rocks and how they form on the NGScience website. QuickCode: Q5F4
How Do Rocks Form?
Scientists who study rocks, called geologists, often classify rocks by how they form. They can be classified into three main groups – igneous rocks, sedimentary rocks and metamorphic rocks.
Beneath the surface of the Earth, temperatures can be very hot. It can be so hot that rock exists in a liquid (molten) form, called magma. Igneous rocks form when magma cools and returns to a solid state.
Granite forms when magma cools slowly beneath the Earth’s surface.
Sometimes, magma cools slowly beneath the Earth’s surface and forms rocks such as granite. Other times, heat and pressure cause magma to break through openings in the Earth’s surface, called volcanoes. The magma flows onto the Earth’s surface as lava. The lava cools rapidly and forms solid rocks such as basalt.
Think Deeply
How are magma and lava similar? How are they different? Draw a picture or create a Venn diagram.
Basalt is an igneous rock that forms when lava cools rapidly.
sandstone On the surface of the Earth, weathering and erosion break down rock and the remains of living things into small particles. Wind and water transport these particles to areas of dry land, into rivers, lakes and the ocean. Groups of these particles settle to form sediments. Over many years, layers of sediments form and are pressed together forming new rock called sedimentary rock. Common types of sedimentary rock include sandstone and limestone.
In sedimentary rock, it is often possible to see the layers of sediment from which they are formed.
layers of sedimentary rock limestone
Metamorphic rocks are formed when igneous and sedimentary rocks are subject to heat and pressure beneath the Earth’s surface. Over time, the heat and pressure cause the rock to change form. The new metamorphic rock that forms has different properties from the original rock. Heat and pressure beneath the Earth’s surface can cause limestone, a sedimentary rock, to change to marble, a metamorphic rock. Slate is another type of metamorphic rock. It is formed from the sedimentary rock, shale.
Think Deeply
How is the formation of metamorphic rocks similar to the formation of igneous rocks?
Slate is a metamorphic rock formed from shale.
Pink and gray layers of the metamorphic rock, gneiss.
Marble is a metamorphic rock formed from limestone.
A Closer Look The Rock Cycle
Over millions of years, the weathering of rocks and soil on the Earth’s surface along with heat and pressure beneath the Earth’s surface cause rocks to continually change from one form to another. This process is called the rock cycle.
igneous rock
Trace the rock cycle diagram. With a classmate, discuss how rocks are formed at each stage.
AB Activity 8.3
sedimentary rock
