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  • Sara Thompson

How to Grow Geodes in Eggshells

By Sara Thompson

Special to the Enterprise

Eggs are a sign of new birth and used often in springtime, especially around the Easter holiday. Many families will paint eggs or make egg dishes, but have you ever made a mock geode with an egg? This colorful home experiment is a mixture of chemistry and geology and is fun for the whole family.

Supplies needed: Water and a means to boil it, empty eggshells, Epsom salt, liquid glue, paintbrush, and optional food coloring and heat safe cups.

The first thing is to clean out the eggs. Try to crack the shell close to the narrow end so you have the larger end for the geode. Pour out the contents of the egg, so you’re not wasting the egg, feel free to use the insides for breakfast. Clean out the membrane from the inside of egg. Pouring hot water from the sink tap can help, but using your fingers scrape as much of the membrane out, otherwise your geode might mold and turn a dark color. When cleaned out, use a paintbrush to brush some liquid glue onto the inside of the egg. Sprinkle a pinch of Epsom salt onto the glue to help the crystals grow later. Set the eggshells aside and wait for the glue to dry.

Next, have an adult boil around a ½ Cup of water. You can use a microwave or a stovetop. When the water is boiling add Epsom salt a little at a time. After each addition of Epsom salt, stir the solution until all of the salt crystals have dissolved, do this until no more crystals dissolve, you will use approximately ½-¾ Cup of Epsom salt. If you are using one color for your geodes add the food coloring now, but if you want to use more than one, carefully pour the solution into separate heat safe cups for adding the color.

Now you can pour the colorful solutions into the eggshells. The liquid and the shells will be hot, so place them on paper towels in a tray, or keep them in the egg carton so they do not roll around. Once the solution has been poured into the eggshells you just need to sit and wait. As the liquid cools, the Epsom salt crystals in the solution will begin to crystallize, using the dry crystals sprinkled in earlier as anchors. It can take a few hours for the crystals to fully appear, but you can also wait overnight. The longer you wait the larger the crystals will be. Once the liquid is cool enough and you are happy with your crystals, you may discard any remaining liquid. Now you will have a colorful eggshell that looks like a geode.

Even though these are not true geodes, they will dazzle any rock lover with their colorful crystal structures inside the shell. Also, any home scientist will have fun dissolving solids into a liquid and watching them cool and crystallize.


Exploit's coming events:

• Big Day of Giving is less than a month away! Please consider contributing to Explorit on May 5th and help us celebrate 40 years of hands-on science education in the community!

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• A Membership to Explorit grants the recipient free visits to Explorit’s regular public hours, discounts on events, summer camps and workshops, and gives you ASTC benefits to visit other museums throughout the world. To purchase or for more information visit or call Explorit at 530-756-0191.


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