A couple of week ago we decided to make our own geodes, using plastic eggs. I didn't know whether the crystals would form on the plastic, but I thought it was worth a try.
- plastic Easter eggs (or real egg shells)
- Water
- Food coloring
- Something to mix in that will hold hot water
- Plastic cups
- Epsom salt (magnesium sulfate), alum (aluminum potassium sulfate). Borax (sodium tetraborate), salt, sugar...
Make supersaturated solution by heating water until boiling. Stir in your solid (Epsom salt, alum, etc.), one spoonful at a time. Your solution should be clear. Heat it up more if all the solid won’t dissolve. Add food coloring, and let cool for about 10 minutes. We color coded ours so we could tell which crystal was what substance.
Green and blue eggs are Epsom Salts, purple and orange are table salt, and yellow and pink are Borax.
Carefully fill the plastic eggs with the supersaturated solutionLeave the plastic eggs with the supersaturated solution undisturbed for several days or longer.After a few days, you should start to see crystals forming inside your eggshell. When you can, close the plastic eggs and let sit until dry.
 |
A week and a half later, our geodes are crystallized and ready to show you. |
 |
| Open them up and this is what you see. |
 |
| These are the Borax crystals. |
 |
| These are the table salt crystals. |
 |
| These are the Epsom Salts crystals. |
 |
| The one side of the Epsom salt "geode" made one very large crystal. |
 |
| The rest of the Epsom salt crystals were like this. |
 |
| We also put some Borax crystals in a regular egg for comparison. The crystals were thicker in the real egg, but even so, I thought the plastic eggs were successful and the boys like pretending they are geodes and "cracking" them open. |
