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Glow in the Dark Crystal Geode

Fun Crystal Growing Project

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The geode glows brightly after being exposed to light.

The geode glows brightly after being exposed to light.

Anne Helmenstine
It's very easy to make a glow in the dark crystal geode. The 'rock' is a natural mineral (eggshell). You can use one of several common household chemicals to grow the crystals. The glow comes from paint, which you can get from a craft store.

Glow in the Dark Geode Materials

  • eggs
  • glow in the dark paint (I used GlowAway™ washable glowing paint)
  • very hot water (I used my coffee maker)
  • borax, alum, epsom salts, sugar, salt, or use another crystal recipe
  • food coloring (optional -- I used neon green coloring)
Prepare the Glowing 'Geode'
  1. There are two ways to crack your eggs. You can carefully crack the top of the egg by tapping it on a countertop. This will give you a deep geode with a smaller opening. Alternatively, you can crack the equator of the egg or carefully cut it with a knife. This will give you a geode you can open and put back together.
  2. Dump the egg or make scrambled eggs or whatever.
  3. Rinse out the inside of the eggshell with water. Peel away the interior membrane so you are left with only the shell.
  4. Allow the egg to air dry or carefully blot it dry with a paper towel or napkin.
  5. Use a paintbrush, swab, or your fingers to coat the inside of the eggshell with glowing paint.
  6. Set the painted egg aside while you mix the crystal-growing solution.
Make the Crystal Solution
  1. Pour hot water into a cup.
  2. Stir borax or other crystal salt into the water until it stops dissolving and you see some solid at the bottom of the cup.
  3. Add food coloring, if desired. Food coloring does not get incorporated into all crystals (e.g., borax crystals will be clear), but it will stain the egg shell behind the crystals, giving the geode some color.
Grow the Crystals
  1. Support the shell so that it won't tip over. I made a little nest for mine in a crumpled napkin that I set inside a cereal bowl.
  2. Pour the crystal solution into the shell so that it is as full as possible. Don't pour the undissolved solid into the eggshell, just the saturated liquid.
  3. Set the shell somewhere where it won't get knocked over. Allow crystals to grow for several hours (overnight is shown) or as long as you like.
  4. When you are satisfied with the crystal growth, pour out the solution and allow the geode to dry.
  5. Phosphorescent paint is activated by exposing it to bright light. Black light (ultraviolet) produces a very bright glow, also. The duration of the glow depends on the paint you use. My geode glows for about a minute before it needs to be recharged. Some paints will produce geodes that glow for a few seconds. Other paints may glow for many minutes.
  6. Store your geode in a dry location, protected from dust.

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