I remember as a kid my Grandma used to have a bookshelf lined with Geodes. They were absolutely magical to me. Like a key to the land of Dwarves and Fairies (I used to think that was how crystals were made). Recently my kids asked how to make a Crystal Geode. I don’t think I have been this excited for a science experiment in a while. This simple science experiment definitely brought out the kid in me!
What is a Geode?
A Geode is a hollow sedimentary rock that has beautiful crystals inside. In the Greek language, geode means “shape of the earth”. Geodes are round like earth or oblong like an egg. They are formed over millions of years through exposure to heat and water. It can take hundreds of millions of years for the space inside a geode to be filled. Once a geode which is completely filled with crystals is called a nodule.
Items Needed to Make a Crystal Geode
- Rock Salt
- Sea Salt
- Eggs or Flat Rocks
- Food Coloring
- Clear Plastic Containers
- Any other substances that can be tested for crystallization such as alum or sugar.
(we made the ones pictured above using borax).
How to Grow Crystals in Eggshells:
When setting up your experiment the first thing you are going to want to consider is where you are going to place your eggs once they are cracked. I know that seems silly, but trust me, it can be very frustrating to crack your eggs in half only to have the little hands that are helping you shatter that shell. Even if it is a learning experience for them, it will save your sanity to have a designated spot determined before you start. Also this experiment will take 3-7 days so make sure that this spot can be easily observed, but not easily gotten into. Borax and alum are both chemicals so you want to make sure that you are able to control when and how your child interacts with this experiment.
When cracking your eggs for your geodes you are going to want to use a butter knife and start by gently tapping along the edge. Once you have a small crack in the edge of your egg use your butter knife in a sawing motion until it has cut the egg completely in half. While this is messy it is insanely easy!
Once your eggs are sawed in half you are going to want to heat up some water to not quite boiling and pour it into your containers for mixing. We put 1/2 cup of hot water, and 1/2 cup of borax. This dissolved quickly. Once the borax is fully dissolved add in whichever food dye coloring you desire. Livia is all about pink so we made some pretty pink princess crystals…
Then we place your eggs into your solutions and wait for the liquid to evaporate. This took approximately 7 days for us which did feel like forever.
Our homemade geodes turned out AWESOME! They were good and sturdy which was perfect for letting the kids explore with bright vibrant crystals.
The kids were fascinated with the way they egg crystals looked and felt. Meatball was particularly fascinated with the parts of the geode that formed white despite the coloring added to the mixture.
Using his magnifying glass to study the crystals up close the kids also drew out the details within the geodes that they observed. One of the kids noticed that the egg shells fit together and that the crystals were formed in the empty spaces which led to discussion on how real geodes are often formed from animal burrows or tree roots.