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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Sure – anything that will hold your crystal solution will work just fine!
Can you use something else besides egg shells?
The crystals in this experiment are made from alum, so that is the only substance you can use. But you have other options for growing crystals in the other experiments.
We cannot buy alum anywhere in our town. Is there any other substance we can use?
Im going to do this for Easter decorations
No, pipe cleaner won’t provide the desired effect. You’ll need to use clean egg shells.
would a pipe cleaner work instead of an egg shell???
Great question! The crystals will form very quickly if the water is really hot or extremely saturated. Go ahead and try it both ways, then note the differences!
what happens when you get the water too hot and too saturated?
If you put the solution in a oven somewhere in between 120 and 200 degrees Fahrenheit would the solution evaporate and form crystals quicker?
Thanks
-Garrison
Hmmm… I have two thoughts. Either the bulk powder you bought isn’t pure alum (there’s something else mixed in), or the solution wasn’t saturated and you just need to mix in more powder to make it work. You can heat the water so it can absorb more powder to be really sure it’s super-saturated. Let me know how it goes!
We made alum crystals with alum powder from the grocery store and it worked fine, but later we bought alum powder from the bulk barn and have been unable to make crystals, we have tried a few times and never any crystals. Do you have any idea why?
Yes it does!
does saturated salt work
-Gabe
My daughter suggested an egg carton would be a great place to store the shells while the crystals form.
Yes of course!
can i use a cup instead of eggshells
You can try – or you can dissolve the shell in vinegar, but that may also wear down the crystals. Try it?
Can you chip away the eggshell when the geodes have formed? Or will that mess up the geode?
Do you mean the alum? It’s int he spice section or the gardening area.
can you by it at target?
It’s just a place to grow the crystals in. 🙂
I didn’t try this but I’m going to is the eggshell special? I mean does the aluminum chemically bind with the aluminum or is it just a place to keep the crystals.
Liam
Crystals start growing when the molecules in a liquid cool down and harden. Molecules in the liquid attach together as they cool, and when they form a repeating pattern, it’s called a crystal. In nature, crystals form when magma cools slowly. Crystals also form when water evaporates, like with salt crystals.
why do the crystals form
We heat it up to dissolve the crystals into the solution, so just warm it up until the bits on the bottom are gone.
How warm does it need to be?