Grade by Grade
E. Earth and Space Systems · Rocks, Minerals, and Geological Processes

Rocks and Minerals: What's the Difference?

E2.3 A1.2 A1.5About 40 minutes
Learning goals
  • I can explain the difference between a rock and a mineral.
  • I can name some common minerals, like quartz, feldspar, mica and halite.
  • I can observe a rock closely and describe its colour, lustre and texture.
  • I can record my observations like a scientist, with drawings, labels and science words.

Words to know

mineral
A natural, non-living solid that is the same all the way through. Minerals often grow as crystals. Examples: quartz, mica, halite (salt).
rock
A natural solid made of one mineral or a mix of minerals (and sometimes bits of shells or other things).
crystal
A solid with flat sides and a regular shape, because its tiny parts are lined up in a repeating pattern.
lustre
How a mineral shines in the light: metallic (like metal), glassy, pearly or dull.
texture
How a rock feels and what its grains look like: rough, smooth, sandy, big crystals or tiny grains.
geologist
A scientist who studies rocks, minerals and how the Earth changes.

Every rock has a story

Pick up a rock from your driveway, a park or a beach. It might look plain. But that rock may be millions or even billions of years old! It may have been melted deep inside the Earth, or pressed together at the bottom of an ancient sea.

In this unit you will learn to read the story in a rock, like a geologist. A geologist is a scientist who studies rocks, minerals and how the Earth changes. Let's start with two important words: rock and mineral.

Remember from Grade 3

In Grade 3 you learned that soil is partly made of tiny bits of rock. Weathering breaks big rocks into smaller pieces. Sand, silt and clay are rock bits of different sizes. Now you will look at the rocks themselves, and at the minerals they are made of.

What is a mineral?

A mineral is:

  • natural (made by nature, not in a factory),
  • non-living (it was never alive),
  • a solid,
  • the same all the way through. If you broke a piece of quartz in half, both halves would still be quartz.

Many minerals grow as crystals, with flat sides and sharp edges. Their tiny parts line up in a repeating pattern, a bit like bricks in a wall.

Scientists know of thousands of minerals, but only a few are very common. Here are some you will meet in this unit:

  • quartz: often clear or white, glassy and very hard
  • feldspar: often pink, white or grey; very common in rocks
  • mica: flat and shiny; peels into thin, see-through sheets
  • halite: the mineral we use as table salt
  • calcite: the mineral that makes up limestone and seashells
  • amethyst: a purple kind of quartz. Amethyst is Ontario's official mineral, and it is found near Thunder Bay.

What is a rock?

A rock is a natural solid made of one or more minerals. Some rocks also have bits of shells, plants or other rocks inside.

Think of a chocolate chip cookie. The cookie is like a rock. The flour, chocolate chips and oats are like the minerals inside it. You can see the chips in the cookie, just as you can often see different minerals in a rock.

A mineral is the same all the way through. A rock is often a mix.

A close-up of a piece of granite showing pink, glassy grey-white and black mineral grains.
Granite is a rock made of several minerals you can see, like chips in a cookie: pink feldspar, glassy grey quartz and black mica. AI-generated image
cookie = ROCKa mix of ingredientsis likegranite = ROCKa mix of mineralsfeldsparquartzmica (flakes)chips, oats = "minerals"
A chocolate chip cookie is a mix of ingredients, just as a rock like granite is a mix of minerals. Each mineral piece is the same all the way through.
RockMinerals you can often see in it
granitequartz (grey or clear and glassy), feldspar (pink or white), mica (shiny flakes), and often a dark mineral
sandstonemostly grains of quartz sand, glued together
limestonemostly calcite, often with bits of shells
rock saltmostly halite
Rocks are made of minerals. Some rocks are mostly one mineral; others are a mix.
a rock (granite)one mineral crystal
Left: a rock (granite) is a mix of different mineral pieces fitted together. Right: a single mineral crystal has flat faces and the same material all the way through.
Worked example

Let's sort: rock or mineral?

Sort these: granite, quartz crystal, sandstone, a gold nugget, a halite (salt) crystal, conglomerate (a rock made of pebbles cemented together).

  1. Ask: "Is it the same all the way through, or is it a mix of pieces?"
  2. Quartz, gold and halite are each one substance, the same all the way through. They are minerals.
  3. Granite is a mix of quartz, feldspar and mica, so it is a rock.
  4. Sandstone is many sand grains glued together, and conglomerate is many pebbles cemented together. Both are rocks.

Minerals: quartz crystal, gold nugget, halite crystal. Rocks: granite, sandstone, conglomerate.

How to observe like a geologist

Geologists start by looking closely. They describe:

  • Colour: What colour or colours do you see? Are there specks?
  • Lustre: How does it shine? Metallic (like a spoon), glassy (like a window), pearly, or dull (like chalk)?
  • Texture: Is it rough or smooth? Can you see grains or crystals? Are they big or tiny?
  • Layers or stripes: Do you see lines or bands?
  • Holes: Does it have small holes, like a sponge?

A magnifying glass helps a lot. Wetting a rock with a little water often makes its colours easier to see.

Worked example

Let's observe a rock together

Maya finds a speckled rock at the cottage. Let's describe it like a geologist.

  1. Colour: pink, white, grey and black specks.
  2. Lustre: the grey bits look glassy. A few tiny flakes are shiny and flash in the sun.
  3. Texture: rough. The pieces are big enough to see without a magnifying glass. They fit together like a puzzle.
  4. Layers or holes: no layers and no holes.
  5. Think: the pink pieces could be feldspar, the glassy grey pieces could be quartz, and the shiny flakes could be mica. This rock is probably granite.

Maya's rock is a mix of minerals, so it is a rock, probably granite. A good observation uses colour, lustre and texture words.

Stay safe, rock hound!

  • Never taste or lick a rock or mineral. Some minerals are harmful.
  • Wash your hands after handling rocks.
  • Collect rocks only with a grown-up and only where it is allowed. Ask before you take a rock from someone's property. In provincial and national parks, the rule is to leave rocks where they are.
  • Stay away from cliff edges, road sides and fast water.
Just for fun

I wanted to tell you a joke about granite...

but I was afraid you'd take it for granite!

Hands-on activity

Start your rock collection

You need: an empty egg carton, a small bag, a magnifying glass (if you have one), a cup of water, an old toothbrush, paper, a pencil, some masking tape and a pinch of table salt.

  1. With a grown-up, collect 6 to 12 different rocks from your yard, a schoolyard, a driveway or a beach where collecting is allowed. Try to find different colours and textures.
  2. Scrub each rock with the toothbrush and water. Let them dry.
  3. Put a small piece of masking tape on each rock and number it.
  4. Put one rock in each cup of the egg carton.
  5. Make a chart with these columns: Number, Colour, Lustre, Texture, Layers or holes?, Rock or mineral?
  6. Observe each rock and fill in a row. Draw your favourite rock and label its parts.
  7. Look at a few grains of table salt with the magnifying glass. What shape are they? (Many grains are tiny cubes, because halite crystals grow in cube shapes.)

Keep your collection! You will test it in the next lessons.

Your turn

1

What is the difference between a rock and a mineral?

2

Name three minerals.

3

Which mineral do we sprinkle on our food?

4

Granite has quartz, feldspar and mica in it. Is granite a rock or a mineral?

5

What does lustre mean? Give two kinds.

6

What is Ontario's official mineral?

7

Why should you never lick a rock to see what it is?

More practice: warm-up

1

True or false: A mineral was once alive.

2

What do we call a scientist who studies rocks?

3

Which mineral peels into thin, shiny sheets?

4

What tool helps you see small grains in a rock?

5

What shape are many grains of table salt?

More practice: on your own

1

Use the cookie idea to explain how rocks and minerals are related.

2

A big grey boulder is made of many tiny grains of calcite stuck together. Is it a rock or a mineral? Explain.

3

Describe the lustre of: a new coin, a window, and a piece of chalk.

4

Why might a geologist wet a rock before looking at it?

5

Sam's chart says "Rock 3: pretty." How could he improve his observation?

Challenge

1

Quartz can be clear, white, pink or purple. Why do you think geologists don't use colour alone to name a mineral?

2

You break a rock in half. One half has pink and grey pieces; the other half has the same pink and grey pieces. Does that prove it is a mineral? Explain.

3

Plan how you would share your rock collection with your class so they learn the most. Name two things you would include.

Check your understanding

Quiz

1.

Which is a mineral?

2.

A rock is...

3.

Halite is the mineral we use as...

4.

A mineral that flashes like a metal spoon has a ____ lustre.

5.

Which is a safe way to study a rock?

6.

Ontario's official mineral is...

For parents and teachers

Big idea (E2.3): Minerals are natural, non-living, solid substances with the same make-up throughout, often forming crystals. Rocks are made of one or more minerals. Classifying starts with careful observation of colour, lustre and texture.

How to help: The rock collection is used in later lessons, so help your child gather a good variety (light and dark, sparkly and dull, layered and speckled). Driveway gravel, garden stones and landscaping rocks are great sources. Encourage precise words instead of "pretty" or "cool" (A1.5, communicating with science vocabulary).

Common difficulties:

  • Thinking "mineral" means vitamins. In science, a mineral is a natural non-living solid. (The minerals in food, like calcium and iron, are related chemical elements, but that is a different use of the word.)
  • Thinking a rock made of one mineral is a mineral. Limestone (mostly calcite) is still a rock: a large body made of many mineral grains.
  • Naming by colour alone. Many minerals come in several colours.

Safety: Never taste rocks; wash hands; follow park rules (rocks stay in provincial and national parks); stay back from cliffs and roads.