Our easy rock investigation, making edible rocks, is a great introduction to different types of rocks and the rock cycle. The Earth is constantly baking, squashing, and melting solid rock into different shapes and textures, but real rocks take millions of years to form, so we’ll demonstrate the rock cycle with chocolate!
Chocolate is perfect for learning about the rock cycle because it can be heated, cooled, and compressed like real rocks. This activity shows you how to create chocolate versions of the three main rock types: sedimentary, metamorphic and igneous. They look good and taste even better!
Edible Rock Investigation
You’ll need:
Grated chocolate – milk and white
Crushed biscuits or more chocolate
Muffin tray
Cupcake cases
Kitchen foil
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 layers pile up, they push down on the lower layers, and over a long time, water is squeezed out of the rock layers 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 top and press down hard to compact the chocolate.
This represents sedimentary rock!
Challenge – can you add a fossil?
Igneous Rock
Igneous rocks form 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.
Make a chocolate igneous rock
This time melt the chocolate. For ease, you could do this in a microwave, or place the chocolate in a cup made from aluminium foil and put 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 when heat or pressure changes sedimentary and igneous rocks underground. These rarely contain fossils.
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 demonstrates both heat and pressure.
Enjoy your 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!
Last Updated on September 18, 2026 by Emma Vanstone
