Our easy rock investigation making edible rocks is a great introduction to different types of rocks and the rock cycle.

rock cycle diagram
Rock cycle diagram

Chocolate is perfect for learning about the rock cycle as it can be heated, cooled and compressed just like real rocks.

This activity uses chocolate to demonstrate how three different types of rocks form.

Image of chocolate igneous, metamorphic and  sedimentary rocks

Edible Rock Investigation

You’ll need:

Grated chocolate – milk and white

Crushed biscuits or more chocolate

Muffin tray

Cupcake cases

Kitchen foil

muffing tray with shaved choclates and crushed biscuits
Ingredients for making edible rocks

Sedimentary Rocks

Sedimentary Rocks form under the sea. Layers of broken rock transported from rivers build up at the bottom of the ocean. The deposited rocks build up in layers called sediments. As more and more layers pile up they start to push down on the lower layers and over a long period of time, water is squeezed out of the layers of rock and salt crystals form. The salt compounds stick the pieces of rock together. Eventually ( sometimes after millions of years ) sedimentary rocks form. This type of rock does contain fossils.

Make a chocolate sedimentary rock

Use the different chocolates and crushed biscuits to make layers in a cupcake case.

Place a small sheet of aluminium foil on the top and press down hard, compacting the chocolate.

This represents sedimentary rock!

chocolate sedimentary rock made by ayers up chocolate and crushed biscuits.
chocolate sedimentary rock

Challenge – can you add a fossil?

Igneous Rock

Igneous Rocks are formed underground where temperatures are hot enough to melt rock into liquid. Igneous rocks do not contain fossils as they would have melted as the rock formed.

Chocolate igneous rock

Make a chocolate igneous rock

This time melt the chocolate. For ease you could do this in a microwave or another idea is to place the chocolate in a cup made from aluminium foil and place it in a bowl on top of a pan of very hot water ( ask an adult to help ).

We left the biscuits in but you could leave these out so the whole thing melts like an igneous rock.

Leave to cool.

Metamorphic rocks

Metamorphic rocks form from sedimentary and igneous rocks that have been changed by heat or pressure underground. These rarely contain fossils.

chocolate metamorphic rock

Make a chocolate metamorphic rock

Metamorphic rocks form from sedimentary or igneous rocks, so this time take half of your sedimentary rock and half of your igneous rock and melt them the same way you did with the igneous rocks.

Leave to cool and squash a little bit. This process has demonstrated both heat and pressure.

Enjoy your edible rocks!!!

image showing chocolate metamorphic, igneous and sedimentary rocks
Edible rocks

More rock investigations for kids

Learn more about how sedimentary rocks form with a sedimentary sandwich.

Rainy Day Mum has some brilliant honeycomb igneous rocks too!

Set up your very own rock lab and identify rocks using simple tests!

Image of different rocks to be used as  part of a rock lab investigation.

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