MINERALS, ROCKS AND SOIL ACTIVITIES

HOW TO LOOK AFTER SOIL

Soil is essential for people.
This is because plants need soil to grow.
We need plants for food and for wood.
Plant roots help fix soil and prevent wind and water sweeping it away.
Plant leaves and branches protect soil from heavy rains.
For this reason, we must protect the plants that grow in soil.

SOIL IS MADE UP OF LAYERS

Soil is made up of three layers, each containing different materials:

• Topsoil: This top layer contains sand, clay, water, air and humus.
• Subsoil: This middle layer contains stones, sand, clay and some water.
• Bedrock: This bottom layer is made up of rocks, and contains very little water.

A: TOPSOIL; B: SUBSOIL; C: BEDROCK.
Photo from Wikipedia

HOW IS SOIL FORMED?

Soil is a mixture of many things.
It forms very slowly over a long period of time.
First, wind, rain and ice wear down rocks into smaller pieces.
Then, the action of animals and plant roots breaks the rocks into even smaller pieces.
Little by little, the pieces of rock mix with the remains of plants or animals.
These remains of living things turn into a dark mixture called humus.
The little pieces of rock mix with the humus to form soil.
There are different types of soils because they are formed from different mixtures of rocks and organic matter.

WHAT IS SOIL?

In many places, rocks are covered by a layer of earth, called soil.
Soil consists of stones, water, air, minerals and the remains of animals and plants.

USES OF MINERALS

Minerals can be used for:

• Construction materials. Gypsum is used to make cement and plaster.
• Obtaining metals. Iron is extracted from magnetite. Copper is obtained from chalcopyrite.
• Making jewellery. Diamonds, rubies and emeralds are used to make jewellery.

MINERALS IN ROCKS

Rocks in the Earth's crust are made up of minerals.
Here are some:

• Quartz: Quartz is very hard. It can scratch glass. It is translucent. It can be white, pink or grey. It is found in granite.

• Feldspar: Feldspar is hard. It is not shiny. It can be different colours: white, green or brown. It is found in granite and clay.

• Calcite: Calcite is soft. It can be scratched with a knife. It can be white, orange or yellow. It is found in marble and limestone.

THE PROPERTIES OF MINERALS

Every mineral is different from all other minerals.
You can identify a mineral by its properties:

• Hardness: a mineral is hard when it is difficult to scratch.
• Lustre: lustre means the way a mineral reflects light. Some minerals are very shiny. Others are not shiny.
• Colour: some minerals are always the same colour. Others can be different colours.
• Shape: Some minerals have a regular shape. Others have an irregular shape.

WHAT ARE MINERALS?

Minerals are natural, solid substances.
All minerals are made up of only one substance.
They can be found as parts of rocks or in their pure state.
Graphite: It is a natural substance.
It is a mineral.
It is soft and when we press it, layers slide off and leave marks on the paper.

Graphite.

We use graphite when we write with a pencil.

USES OF ROCKS

Rocks are used for many different things:

• Obtaining energy. Petroleum provides fuels, such as petrol and diesel.
• Making construction materials. Bricks and tiles are made from clay. Marble, granite and slate are also used in construction.
• Industrial uses. Factories make plastics, paints and fertilisers from petroleum.

WHERE CAN YOU FIND ROCKS?

Rocks can be found near the surface of the Earth or deep beneath the ground.

• Mines. These are places where rocks and minerals are extracted from deep beneath the ground. Miners reach the rocks by travelling through shafts and tunnels.

• Quarries. These are places where rocks are extracted from near the surface of the Earth.

WHAT ARE ROCKS LIKE?

All rocks are made up of minerals, but there are many different types:

• Some rocks are formed by just one mineral. Marble is made entirely of calcite.
• Other rocks are made up of several minerals. Granite is made up of quartz, feldspar and mica.
• Some rocks, such as limestone, sometimes have shells and sea creatures in them.
• Some rocks are hard (marble). Others are soft (clay). Others are liquid (petroleum).

WHAT ARE ROCKS?

Rocks form the solid part of the Earth.
They are found everywhere in nature.
Some rocks are dark (basalt).
Others are light in colour (limestone).
Some rocks are formed by large grains (granite).
Others are formed by fine grains (clay).

Rocks in nature (from wikipedia)

Clay: fine grains (from wikipedia)

Limestone: light in colour (from wikipedia)

Granite: large grains (from wikipedia)

Basalt: dark colour (from wikipedia)

REMEMBER

ROCKS AND MINERALS

Rocks and minerals have many uses.
For example, pencils are made up of a mineral called graphite.
Roof tiles are made of a rock called clay.

Pencil (photo by Saurabh R. Patil (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons) 

Graphite (photo by Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons)

Roof tiles (photo by Procsilas Moscas (Flickr) [CC-BY-2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons)

Clay mineral (photo from Wikipedia)

SOIL

Soil is the top layer of the Earth's surface.
This is where plants grow.
Some animals, such as rabbits and worms, make their homes in soil.

Soil (photo from Wikipedia)