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Saturday Science: Crystal Egg Geode

Saturday Science: Crystal Egg Geode

Saturday Science: Crystal Egg Geode

This holiday, don’t just dye eggs, create colorful crystal egg geodes that sparkle and shine. During an egg hunt, they might even be too easy to find! This week’s EGG-cellent Saturday Science, found on Martha Stewart, Feels Like Home Blog and Steve Spangler Science, explores how crystals form inside geodes.


  • Plastic eggs or real egg shells (cut in half)
  • Small paintbrush
  • White glue
  • Alum powder
  • Craft stick or spoon
  • Plastic or glass container
  • Egg dye
  • Hot water
  • Latex gloves
  • Drying rack or newspaper


  1. Whether using plastic or real eggs, make sure the inside of the eggshell is clean and dry.
  2. With a small paintbrush, apply white glue to the inside edges of each eggshell and sprinkle with alum powder until completely coated. Set eggshell halves aside to dry overnight.
  3. The next day you can prepare your growing solution! Have an adult help you pour 2 cups of almost-boiling water into your plastic or glass container. Put on your latex gloves and use a craft stick or spoon to mix in an entire packet of powdered egg dye.
  4. Add 3/4 cup of alum powder to the solution and stir until completely dissolved. If there are remaining crystals in the bottom of the container, place the solution in the microwave for a few minutes to dissolve them. 
  5. Let the solution cool for about 30 minutes. 
  6. Submerge one of the dried, alum-coated eggshells in the solution, allowing it to rest on the bottom of the container with the inside of the shell facing up.
  7. Set the container aside and allow the crystals to grow undisturbed for about 12-15 hours. The longer you leave the eggs shells in the solution, the larger your crystals will be. 
  8. The next day, put on your latex gloves again and have an adult help you remove the geode from the container. Be careful! Wet crystals are very fragile! 
  9. Place your geode on a drying rack or newspaper and allow to dry completely before handling.


Wondering how eggs shells and alum powder could create such a colorful and sparkly crystal egg geode? Let’s explore! 

The process your crystal egg geode went through is called sedimentation. 

According to Steve Spangler Science, when the alum powder dissolves into the hot water, its particles get suspended in the solution. But, as the water cools, they drop towards the bottom of the container and settle on the egg shell where they easily attach to the alum powder glued to the surface or the egg shell. Overnight, water molecules evaporated from the container, which caused the particles to crystallize. The more water evaporated, or the longer you left the egg shells in the solution, the bigger the crystals! To learn more about how crystals form, try our Crystal Suncatchers experiment. 

Want more Saturday Science? See all of our at-home activities on the blog or Pinterest

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Categories: Science
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