‘I’m not a Scientist..!’ – Crystals Activity 2: Chocolate Crystal Geode

By Farhin Begum

Hello to all you scientists and non scientists!

I am so glad you came back for some more crystal action! The last activity I did was an exciting experiment on growing your own Egg Geodes, which sadly went terribly WRONG! If you’d like to find out how I got on (and how to do it properly) you can find it here.

This is a brand new and exciting activity which this time worked! I will be showing you how to achieve a Chocolate Crystal Geode and kids can join in the fun too. More importantly, this one is edible! (If you have a massive sweet tooth).




Your chocolate geodes should look something like this at the end of the activity.


Let’s get started!




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You will need…

  • Sugar (3 cups)
  • Water (1 cup)
  • Spoon
  • Food colouring of your choice
  • Cup measure
  • 2 Bowls (1 big & 1 small)
  • Kitchen towel or cloth
  • Plain Flour
  • Pan
  • Kitchen foil
  • Baking sheet/paper
  • White Chocolate
  • Cocoa Powder
  • Biscuits or Cookies (Optional)


Step 1 –  All you need is water and sugar


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First put your pan on a medium sized stove and set it on medium heat, then add your 1 cup of water into the pan along with 3 cups of sugar.





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Make sure you keep stirring the sugar mixture until it dissolves or the sugar will burn!

It should look like this –>





Step 2 – Blue, Red, Purple!


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Next you can add food colouring of your choice to give the crystals some colour. If you have food colouring paste you will get stronger pigmented result at the end.

I used 5 lids of red and 3 lids of blue – it turned into this beautiful dark purple colour.



Step 3 – Make your mould!


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To make your geode mould half fill a big bowl with plain flour. Then  make a hole in the middle and insert the small bowl into the big bowl so that the bowl doesn’t move about. Put more plain flour in the small bowl and shape your mould by pressing/pushing the flour down with your fingers. If you’re happy with how your mould looks, put kitchen foil on top of your flour mould and gently press it down. Then add another piece of foil on top so that the sugar mixture doesn’t leak through into to the flour!


Step 4 – Leave it to set


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Half fill the mould with your sugar mixture.


Then cover the bowl with a kitchen towel or cloth and leave it for about a week.



CC-BY-sciencemadesimple (Left to right) Day 2, Day 4 & Day 6.

(Left to right) Day 2, Day 4 & Day 6.

If you check on it every two days or so will be be able to see the crystals gradually growing.

I made two geodes because I had lots of the sugar mixture left. I advise that you do the same as only one of them was a success!



Step 5 – Waiting a little longer…

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On day 7. gently break the top of the sugar mixture and let them sit on a baking sheet to dry over night. (left plate of crystals).

Lift up the foil and pour the remaining sugar mixture out then gently peel the foil off the back of the geode.

After you’ve done that, tilt the geode upside down and place it on top of a cup where you should leave it to dry for 2 days.



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After two days, get one clean piece of baking paper and lay everything out nicely. Flip all the crystals and the geode over so that they can get dry evenly on the other side too, leave this for a day to set.

Remember that I said that food colouring paste works better than regular food colouring? This is why my geode has turned pink instead of staying the nice purple colour I was aiming for.

Step 6 – Awesome crystal results

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You can now hold your unfinished crystal geode without it sticking to your hands, beautiful right?

You can either leave your geode like this, or you can go on to the next step and make it look like a real geode.






Step 7 – Cover it in White Chocolate


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Break your white chocolate bar into a small bowl.

Put it in the microwave for 20 seconds and stir it well, keep doing this 4-5 times until the chocolate is runny.


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Tilt your geode upside down on a cup then start pouring one layer of chocolate until it’s fully covered. With a spatula, scoop up the chocolate sitting under the drippy geode to re-use later.

When the first layer has cooled down for 5-10 minutes, start pouring another layer on top then leave it to set for an hour.

Step 8 – This could get very messy


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Remelt any white chocolate drips and spare white chocolate and add any biscuits or cookies that you can sacrifice for this activity along with one table spoon of cocoa powder and mix away!

I added too much cocoa powder (2 tablespoons) that made my mixture very dry! Then a added some water because I panicked and then it was too runny! So I stuck my whole hand in the mixture and worked with it until was just right!

Step 9 – And a sprinkle of Cocoa powder


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When you get the right texture for your geode pour it on top of the white chocolate layer.

Leave it to set for a day then sprinkle some cocoa powder on top.

Dust off the excess powder so it gives you that ‘rocky’ look.



Step 10 – The end result!

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After you have let it set for the day, get a knife and neaten up the edges so it looks more like a real geode.

And tada! Here is the finished result!








Where I got this idea?




I got this awesome idea from a YouTube channel called ‘How To Cook That‘, they can show a better demonstration if you did not understand this one properly!

They also have a website which explains this activity step by step.






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Posted in Activity, Chemistry, Exploring Science, Geology
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