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How to make rock candy geodes

Rock Candy Geodes Recipe

  • Total Time: 26 minutes
  • Yield: 12 candies 1x


There are two parts to this recipe. First is the hard shell of the geode and second is the crystal inside. I’ve broken them apart in this post card and I’ve also written them out separately below this recipe card.



Ingredients for the hard shell:

  1. 1 lb marshmallows
  2. 1 lb confectioner’s sugar
  3. Shortening
  4. Gum-Tex powder
  5. Black food coloring
  6. Peppermint flavoring extract

Ingredients for the crystals:

  1. ½ cup of water
  2. 2 cups granulated sugar
  3. Blue food coloring
  4. Raspberry flavoring extract

Kitchen tools you’ll need:

  1. Silicon cake pop molds
  2. Tinfoil
  3. Candy thermometer  (this is the one I use)


Instructions for the hard shell:

  1. Melt the marshmallows in the microwave. Place it on high heat for 1 minute and 20 seconds but take out and stir every 15 seconds.
  2. Add in the confectioner’s sugar and mix until well blended and cool enough to be kneaded.
  3. Coat a portion of your countertop or board with some sugar, then coat your hands with shortening. Start kneading the sugar dough.
  4. When your dough is flexible enough, sprinkle a little Gum-Tex on top and knead again until well combined. The role of Gum-Tex in this process is to help ensure your sugar dough holds its shape.
  5. Cut the gum paste in two and add in the flavoring.
  6. Set aside one half of the gum paste and add food coloring to the other half. I mixed a few drops of black coloring with water to lighten the color a bit. This is to make the geode appear grayish to achieve a more realistic rock color.
  7. Leave both for at least 2 hours.
  8. After 2 hours, roll out both the white and colored gum paste.
  9. Wet the colored gum paste lightly and stick it to the white one.  The white part will serve as the inner lining of the geode.
  10. Roll and cut it according to the size you need for your molds.
  11. Line the molds with foil for easier removal of the shells later.
  12. Press the gum paste into your mold and let it harden in a warm and dry area for 24 hours. The white side should be the one showing on top when you mold your gum paste. The bottom part, which is the colored side which will be the exterior of the rock later on.

Instructions for the crystals:

  1. Make a supersaturated sugar solution by boiling together ½ cup of water and 2 cups of sugar over medium heat.
  2. Bring to a boil and ensure your mixture reaches 237 degrees Fahrenheit using a candy thermometer.
  3. Remove the pan from the heat and add in the flavoring extract and food coloring. Let it cool for a bit.
  4. Set the molds in tinfoil with the gum paste shells still on it. Make sure the size of the tin foil is enough to cover each mold later on.
  5. Pour the cooled syrup into the gum paste shells.
  6. Slowly wrap the tinfoil around the mold and fold it to ensure that the gum paste shells and syrup are completely wrapped.
  7. Leave in a warm place undisturbed for at least one week. This should be enough for the crystals to grow bigger, but you may leave it a few days longer if you want more crystals to form.
  8. Unwrap the molds and turn upside down to drain the excess liquid. Carefully release each shell and leave unturned for a couple of days to dry.
  9. Your geodes should be ready after two days of drying. Serve and let the kids enjoy!
  • Prep Time: 6 minutes
  • Cook Time: 20 minutes
  • Category: Candy
Cook Til Yummy