Geodes are formed from gas bubbles in flowing lava. Up close, a geode is a crystallized mineral deposit that is usually very dull and ordinary-looking on the outside. When you crack open a geode, however, it’s like being inside a crystal cave. We’ll use an eggshell to simulate a gas bubble in flowing lava.
We’re going to dissolve alum in water and place the solution into an eggshell. In real life, minerals are dissolved in groundwater and placed in a gas bubble pocket. In both cases, you will be left with a geode.
Note: These crystals are not for eating, just for looking.
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