Do Try This At Home | Rock Detectives

Use bits from around the house to investigate the rocks on your doorstep.

Welcome back to Do Try This At Home - our series of super-fun weekly science activities.

Our building is closed right now, but that doesn't mean we can't do some science at home.


Have you even picked up a rock and wondered what it was made of? Or how old it was?

Some of them are millions of years old! But how are they made? And are different rocks made of different things?

Rocks are all around us, so let's study them.

This activity will show you the tests you can do to become a rock detective!


At home!

Who for


You will need

  1. A few different rocks. We had a look around the garden, but you might have some in your house or collect some whilst on your daily exercise!

  2. Some vinegar or lemon juice. We're going to see if we can make our rocks fizz.

  3. A finger nail (your own is fine!) and an iron nail to test the hardness of your rocks.

  4. A bowl or cup of water to see if any of your rocks float.

  5. Maybe a magnifying glass. You don't have to have one, but might help you look for fossils!

Geology of Bristol

Geology means "study of earth", and people who study rocks are called 'geologists'.

You find different rocks in different places.

This map shows us the types of rock that can be found in southern Britain. Each colour is a different type of rock.

Most of the rocks under Bristol are limestones, sandstones and mudstones.

These are all sedimentary rocks.


Types of rock

There are three main types of rock, made in different ways.


Sedimentary rocks are formed when lots of "sediment" (small bits of rock, plants and animals) collects in rivers or on the sea floor. As the layers build up they get squashed and over time form rock. Sometimes you can even find fossils in these rocks!


These rocks started life in a volcano, how cool is that? Igneous rocks are pieces of magma or lava that have cooled down.


Sedimentary or igneous rocks can get crushed under lots of other rocks and heated up by the inside of the Earth. This makes them change ('metamorphose') into a new type of rock known as a metamorphic rock. 'Metamorphose' is the same word scientists use for how a caterpillar turns into a butterfly!

Get curious!

Now it's your turn to find out what rocks you have.

Carry out the tests below and see if you can work out which rocks you have collected.

This flow chart will help you work out what rocks you have.

How to... a 'fizz test'

The 'fizz test' can tell whether the rock contains a carbonate.

Do any of your rocks fizz when you add lemon juice or vinegar? If you can't see a fizz, can you hear it?

If you got a fizz that means your rock contains calcium carbonate.


...look for fossils

Fossils are parts of plants and animals from millions of years ago and have been preserved in the rock.

They might look like shells you find on the beach, leaves from plants or even slightly stranger looking creatures.

Do your rocks have any fossils in them?


...identify crystals and grains

Crystals are shiny and bigger.

Grains are smaller and more rounded.

Can you decide if your rocks are made from crystals or grains?


  • Do all pieces of the same rock look the same?
  • Did you find mostly natural or mostly synthetic rocks where you live?
  • Why do some rocks fizz with lemon juice or vinegar?
  • Which was the hardest rock that you found?


And here's a question asked by Nexie age 7:

'How are rocks and minerals made?'

Share your experiment

We would love to see the rocks you collect.

If you snap a few pictures or a video whilst you're investigating, send them our way - we would love to see them!

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And if you enjoyed this activity, why not try our others in this series?


Image credit: Julian Welsch

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