Egg Geodes

Growing crystals in an egg shell

Several people have written me lately, asking how to make simulated geodes in egg shells. Geodes are pockets of crystals that form in sedimentary and igneous rocks. They start as hollow spaces in rock that is porous enough for water to seep through. The water carries dissolved minerals, which are deposited in the open space, forming a lining of crystals. Most geodes contain quartz crystals, but they can also contain calcite, celestite, and other minerals.

Many rock shops and museum gift shops sell geodes that have been cut, and sometimes dyed to make them more colorful. Sometimes you can buy unbroken geodes, which lets you break them open yourself. That is particularly fun, as you never know how it will look until you open it.

If you don't have a place to collect geodes, you can make quick, easy, simulated geodes by using egg shells for the hollow spaces. I have seen several different recipes, many of which take days, but you can make an egg shell geode in a few hours by using epsom salts for the crystals. We will be using basically the same formula that we used for Growing Crystals from Solution, so you will need:

  • several egg shells, washed and cleaned
  • an egg carton to hold the shells
  • epsom salts, available at pharmacies and grocery stores
  • HOT water
  • a measuring cup
  • a refrigerator
  • food coloring

Start by making an omelet or something else yummy that requires eggs. For the best results, crack the eggs close to the small end of the egg. This leaves you a fairly large egg shell to use. The larger the egg shell, the more crystals you will have. Wash the shell, and remove the skin-like membrane that lines the shell. For short term projects, you can leave this membrane in place, but you should remove it if you plan to keep your geode for a long time, as the membrane tends to mold after a while.

Depending on how many eggs you are going to use, you may not need as much of the solution as we used before. I tried using 1/4 cup of epson salts and 1/4 cup of hot water, and it worked fairly well for 6 egg shells. You want the water to be hot, but not quite boiling. Stir in the epsom salts. If it all dissolves, add another spoon full. If that all dissolves, add some more. You want to reach the point where there are a few crystals that will not dissolve.

Place the egg shells in the egg carton, so they won't tip over and make a mess. Then pour the epson salt solution into the shells.

If you want brightly colored crystals, add a drop of food coloring. You might even try adding small drops of two or more colors to the same shell. Be sure to leave some of them uncolored, because I think the pure crystals are prettier than the colored ones.

Carefully place the egg carton into the refrigerator. Put it in a place where it will not be bumped or disturbed, and let it sit for at least 3 hours. That will give your crystals plenty of time to form.

Once you have plenty of crystals, remove the egg carton from the refrigerator. There will still be liquid in the shells, which you can carefully pour into the sink. Be careful not to let the crystals fall out of the shell as you drain them. Each shell should have a mass of needle-shaped crystals inside. As they dry, they will become even more bright and shiny.


If you do not get crystals, then either your water was not hot enough, or you did not add enough epsom salts. The water should be very hot, so that it will dissolve a large amount of the epsom salts. Then keep adding the salts until no more will dissolve.

You can play with the concentration of the epson salts. Adding more epson salts to the water will give you a denser cluster of crystals, while adding a bit less will give you a better view of the individual crystals. If you used clean egg shells, your crystals should remain bright and shiny for weeks.

brevard wrote on Thu, 03/26/2015 - 16:28:

Very interesting, i'm going to try it at home with my mom and see what happens.

echo mountain wrote on Fri, 10/31/2014 - 18:07:


Helen wrote on Wed, 10/22/2014 - 18:07:

We are now trying this experiment. What I find interesting is that the water cools so quickly once added to the Epsom salt. Why is this? Our salt is dissolving very slowly that my Mom added more hot water from the tea pot. It is very hot, near boiling. She tested it with her finger in the glass and it is no longer hot!

Tiger-Tude wrote on Mon, 02/17/2014 - 23:34:

This is a REALLY AWESOME project, thanks SO much for posting it!!!!!


presto02 wrote on Wed, 01/29/2014 - 14:11:

i already put it in the frige a minit ago

Selfdesign wrote on Wed, 09/18/2013 - 21:58:

I am going to try this experiment it sounds awsome

Anonymous wrote on Mon, 05/13/2013 - 13:46:

The "new" way to crack eggs is on a flat surface. This allows the shell to crack but the membrane to stay intact. For cooking, this is great because the pieces of shell stay out of your food. For this project, it should help by allowing the membrane to stay with the egg's contents when you empty it, saving you the "scraping" step.

Anonymous wrote on Sun, 05/05/2013 - 20:55:

is it supposed to be in the freezer or the bottom of the fridge?

rkrampf wrote on Sun, 05/05/2013 - 21:43:

Put it in the refrigerator, not the freezer.

Anonymous wrote on Mon, 04/22/2013 - 22:15:

hi do you dedicate your life to your work

Anonymous wrote on Wed, 02/13/2013 - 21:32:

Google Egg geode and look for steps with ALUM. This makes amazing geodes and only takes 12/15 hours.

Anonymous wrote on Tue, 01/22/2013 - 18:18:

So, i did this for a science project. I did epsom salts in two eggs, sugar in the next two, and salt in the last two. I use this recipe but insted i did the math and did two teaspoons of each. I waited a day in the fridge and it came out as water...Im confused! did i do something wrong, and can you please help me!

Anonymous wrote on Wed, 02/27/2013 - 00:14:

well it certainly said to use Epsom salts. If you used Epsom salts then maybe the stuff wouldn't be water you should try it

rkrampf wrote on Tue, 01/22/2013 - 21:02:

For the salt and sugar, it should come out as water. For the epsom salts, you should have gotten crystals. Be sure the water is hot enough, and that you are using equal amounts of water and epsom salts. If your epsom salts are large lumps, you may need to add a little extra, to make up for the open spaces between the lumps.

Anonymous wrote on Mon, 01/28/2013 - 12:08:

how long would it take because my science far project is in two weeks and i need to compare egg geodes to some thimg else what should it be.

Anonymous wrote on Sat, 12/01/2012 - 12:22:

When you scrap the membrane it is so hard to get it all out. How do you get your membrane out without breaking the entire egg shell? I left them in the freezer for over 3 hours and they only look like ice-cubes. :( So, and oh yea I didnt get all the membrane out and it made the crystal look all white from the membrane and my project is due in 3 days!! Will I be able to fix them? Can I add food coloring to make the egg look like I got all the membrane out?

Anonymous wrote on Thu, 11/29/2012 - 11:04:

How long dose it take

Anonymous wrote on Thu, 01/03/2013 - 17:50:

It will take a week to be awesome

Anonymous wrote on Fri, 09/21/2012 - 12:57:

using it for my science fair with my best bud william! yea awesome test

Anonymous wrote on Sat, 05/19/2012 - 13:10:

The crystals didnt grow yet and it has been 2 days and it is still liquid.

Anonymous wrote on Mon, 03/19/2012 - 11:43:

Can you use cold water?

Anonymous wrote on Wed, 05/16/2012 - 14:06:

no u cant use cold water u must use warm water

rkrampf wrote on Mon, 03/19/2012 - 14:49:

No, cold water will not work well. Hot water dissolves more of the Epsom salts, to make a supersaturated solution.

Anonymous wrote on Mon, 03/19/2012 - 09:11:

Can you do the expriment with the yolk and the white?

Anonymous wrote on Tue, 01/10/2012 - 23:42:

I would love to try this but we are allergic to eggs. Can we use any other container perhaps a plastic Easter egg?

Anonymous wrote on Tue, 01/22/2013 - 18:43:

You can use a cup or anything it really doesnt matter if its an egg shell or not

Anonymous wrote on Mon, 03/19/2012 - 09:06:

I guess so!

rkrampf wrote on Wed, 01/11/2012 - 01:02:

Yes, you can use pretty much any container that will hold water. You could even try putting a nice rock into a glass, and then adding the epsom salt solution. You would probably get some pretty crystals growing on the rock.

Anonymous wrote on Thu, 10/20/2011 - 22:14:

Would this experiment work if we blew the egg out of the shell so that the shell was almost intact, and then used potassium permanganate to make the crytals? I'm thinking that if it did work it would look almost like an amythest geode.

rkrampf wrote on Thu, 10/20/2011 - 22:24:

I don't think potassium permanganate would recrystallize quickly, and grow large crystals. You would have better luck using potassium chromium alum for large, purple crystals.

Anonymous wrote on Fri, 10/21/2011 - 21:28:

Thank you for this. Can you tell me where I'm likely to find potassium chromium alum? I'd like to give it a try.

rkrampf wrote on Fri, 10/21/2011 - 22:50:

Do a Google search for "Chromium Potassium Sulfate". You will find quite a few science supply and photographic supply companies that sell it.

welovescience wrote on Thu, 10/06/2011 - 20:05:
This link shows how to make sugar crystals and has some special technique's and a video tutorial.

Thank you for this experiment. My son and I are looking forward to trying them both, the salt and the sugar crystals.

Anonymous wrote on Thu, 09/29/2011 - 23:06:

Is there a recipe out there where the crystals that form in the eggshell harden enough that you can peel the shell off and have the crystal formation stay intact?

Anonymous wrote on Thu, 09/29/2011 - 23:04:

Is there a recipe somewhere where the crystals that form in the shell are sturdy enough that you can peel the shell off later and just have the hardened crystals?

rkrampf wrote on Fri, 09/30/2011 - 07:57:

I suspect that if you let them dry for a few days, you would be able to remove the egg shell from these. I grew some in a plastic cup, and the clump of crystals came right out, and stayed bright and shiny for a couple of months. Eventually, they absorb enough humidity, and start to turn white. Then you just dissolve them, and grow more crystals.

Anonymous wrote on Thu, 02/23/2012 - 19:24:

How many days would it take for them to come out like that because, I have 3 days to scienefair and this is my project.

rkrampf wrote on Sat, 02/25/2012 - 00:21:

The crystals grow in just a few hours. Usually, science fair projects test an idea, so you might think about what you could test with this. For example, you might try using a different amount of epsom salts for each group, to see if the concentration makes a difference in crystal shape.

Anonymous wrote on Sun, 02/26/2012 - 13:59:

thanks man by now i've made a pot with a sugar saturated solution and one with a salt saturated solution and the sugar isint doing anything!!!!!!! but the salt is sittig in pot just crystalating like crazy.Also i am going to sort of bribe the judges with homemade rock candy!!!!LOL!!!!

voj wrote on Thu, 09/29/2011 - 16:18:

coolest experiment ever!!!
can we use sugar instead of epsom salts then eat the sugary ones?

rkrampf wrote on Fri, 09/30/2011 - 07:54:

Hmm. I've never tried it with sugar, but I will now. I suspect it would work with the right recipe.

downingfamily wrote on Fri, 09/30/2011 - 18:43:

Hello Mr Krampf
I've grown some wonderful crystals using sugar!... and best of all you can eat them at the end!!

This trick is, is to let the mixture cool verrrrry slowly. So I used a vacuum flask to do it.
It took a week (well I left it for a week anyway) and the crystals were very large, like the size of one of your American Dime coins and long in length about 1 -2 inches and really thick, and perfectly angular like a rectangle but more beautiful.... i'd describe it as a glass gemstone.

You must try it!.... and then eat it!

Let me know if you need further details

downingfamily wrote on Sat, 11/26/2011 - 04:51:

I'm curious to know if you have tried to make the sugar crystals yet?
If so, how did they turn out?

rkrampf wrote on Sat, 11/26/2011 - 20:40:

Yes, and it works well. Watch the Igneous Sugar video , and use the same recipe.

Anonymous wrote on Fri, 09/30/2011 - 18:36:

I've grown some wonderful crystals using sugar!... and best of all you can eat them at the end!!

This trick is, is to let the mixture cool verrrrry slowly. So I used a vacuum flask to do it.
It took a week (well I left it for a week anyway) and the crystals were very large, like the size of one of your American Dime coins and long in length about 1 -2 inches and really thick, and perfectly angular like a rectangle but more beautiful.... i'd describe it as a glass gemstone.

You must try it!.... and then eat it!

boris_and_ivan wrote on Wed, 09/28/2011 - 17:14:

That is the coolest experiment ever!!

Anonymous wrote on Wed, 09/28/2011 - 11:05:

I'm going to try this one for sure.