Crystals are fascinating for kids and adults too! We created these gorgeous, sparkling eggshell geodes for a homemade growing crystals science activity. We love this science craft with borax crystals, and there are a variety of ways to make them! Learn how to set up this crystal geode experiment. Simple science experiments for kids!


Crystals are fascinating to kids and adults! We created these gorgeous, sparkling eggshell geodes for a homemade crystal growing science activity. We love this science craft with borax crystals, and there are a variety of ways to make them! Learn how to set up this eggshell geode science experiment. Simple science and STEM for kids everywhere.


Cool chemistry for kids you can set up in the kitchen or in the classroom! If you have a rock hound like I do then anything having to do with rocks and crystals is sure to please. Plus, you can sneak in some awesome chemistry.

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Growing crystal geodes with borax is a simple way to learn about crystals, the re-crystallization process, making saturated solutions, as well as solubility! You can read more about the science behind our eggshell geode experiment below and find out a few facts about geodes.

Eggshell geodes for chemistry and geology


  • From the outside most geodes look like common rocks, but when they are opened up the sight can be breathtaking.
  • Geodes have a durable outer wall and a hollow space inside, which is what allows the crystals to form.
  • If a rock feels lighter than that surrounding rocks, it may be a geode.
  • Most geodes contain clear quartz crystals, while others have purple amethyst crystals. Geodes can also have agate, chalcedony, or jasper banding or crystals such as calcite, dolomite, celestite, etc.
  • Some geodes can be very valuable, especially those that are formed from rare minerals.
  • Geodes form over a very long period of time.

ALSO CHECK OUT: How To Make Candy Geodes

eggshell geode crystals


Luckily you don’t need expensive or special supplies. In fact you can make egg geodes without allum and make them instead with borax powder!

You can also use that borax powder for awesome slime science too! Check the laundry detergent aisle of your supermarket or big box store to pick up a box of borax powder.


  • 5 Eggs
  • 1 ¾ cup Borax Powder
  • 5 Plastic Cups (mason jars work well too)
  • Food Coloring
  • 4 Cups Boiling Water

eggshell geodes with borax powder supplies


STEP 1. Carefully crack each egg so you can reserve lengthwise halves. If you are lucky, you may be able to get 2 halves from each egg.  Rinse each shell and pat it dry,

You need at least 5 halves to make a rainbow assortment of crystal geodes. The egg inside can be discarded or cooked and eaten as you only need the shell. Cooking eggs is a great example of irreversible change!

eggshell geode crystal halves lengthwise

STEP 2. Bring 4 cups of water to a boil and stir in the borax powder until it is dissolved.

There should be a little bit of borax on the bottom of the pan or container that does not dissolve. This lets you know you have added enough borax to the water and that it cannot be absorbed anymore. This is called a supersaturated solution.

making borax saturated solution for crystal chemistry

STEP 3. Set up 5 separate cups in a location where they won’t be disturbed. Pour ¾ cup of the borax mixture into each cup. Next, you can add food coloring and stir.  This will give you colored geodes.

NOTE: The slow cooling of the liquid is a huge part of the process, generally we have found that glass works better over plastic but we had good results this time with plastic cups.

If your solution cools too quickly, impurities will not have a chance to fall out of the mixture and crystals may look disorganized and irregular. Generally crystals are quite uniform in shape.

colored borax saturated solution in cups

STEP 4. Place an eggshell down into each cup making sure the inside of the shell is face up. You want to put the eggshells into the cups while the water is still very hot. Work quickly.

eggshells in borax solution for eggshell geode experiment

STEP 5. Let the shells sit in the cups overnight or even for two nights for plenty of crystals to grow on them! You don’t want to agitate the cups by moving them or stirring them, but make sure to check on them with your eyes to observe the process.

When you see some good crystal growth, remove the shells from the cups and let dry on paper towels overnight. Although the crystals are quite strong, handle your eggshells geodes carefully.

Encourage your kids to get out magnifying glasses and check out the shape of the crystals.

how to make eggshell geodes


chemistry activity with eggshell geodes with borax

Crystal growing is a neat chemistry project that is quick to set up and great for learning about liquids, solids, and soluble solutions.

You are making a saturated solution with more powder than the liquid can hold. The hotter the liquid, the more saturated the solution can become. This is because the molecules in the water move farther apart allowing more of the powder to be dissolved.

As the solution cools down there is all of a sudden going to be more particles in the water as the molecules move back together. Some of these particles will start to fall out of the suspended state they were once in.

The particles will start to settle on the eggshells and form crystals. This is called recrystallization. Once a tiny seed crystal is started, more of the falling material bonds with it to form bigger crystals.

Crystals are a solid with flat sides and symmetrical shape and will always be that way (unless impurities get in the way). They are made up of molecules and have a perfectly arranged and repeating pattern. Some might be bigger or smaller though.

growing eggshell geodes without allum

Look how gorgeous science can be! Kids can easily grow crystals overnight!

Looking for easy science process information and free journal page? 

We have you covered…

Click below to get your quick and easy science activities. 


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Click on the link or on the image for more fun science experiments for kids.


  1. Hi! I love your site. It’s great having the description of what’s going on to share with the kids. How can I use liquid borax instead? Thanks!

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