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Rock Candy Geodes

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We went on a family trip last month to Moab. It is a city in southern Utah that has all of these amazing rock formations. While we were there we went to this fun rock shop where you can buy a geode (a rock with crystals inside) and they will crack it open right there for you. My kids thought this was pretty cool!  Soon after that, I came across a tutorial from How to Cook That explaining how to make a Rock Candy Geode. We had to try it out!  We made ours with fondant and did three different colors of geodes. They turned out great!

Rock Candy Geodes from Teach Beside Me

How to Make Rock Candy Geodes

To make the rock candy geodes you need fondant. You can buy it premade, or make it yourself with marshmallows and powdered sugar. It is quite simple & much cheaper to make yourself. Plus, it tastes a million times better.

Marshmallow Fondant

Marshmallow Fondant Recipe:

1 pound of marshmallows
About 1/2 c. shortening
2 pounds of powdered sugar
4 Tbsp water

In a microwave in a large bowl, melt the marshmallows with 2 Tbsp or water. Heat them 30 seconds at a time and stir in between. It ended up being about 2 1/2 minutes I think. They just need to be all the way melted.

Mix in about half of the powdered sugar with a big spoon. When you have mixed it as well as you can, add in the rest of the sugar. You will want to coat your hands with shortening and just knead it by hand. It is super sticky, so you definitely want your hands greased. And the counter. And any other surface it touches. 😉

If it is really sticky, add little more powdered sugar.. If it is really dry, add in the remaining water. It should be about the consistency of play-dough when you are done.

coloring fondant

We colored half of our fondant and left the other half white. The best way to color fondant is with gel food coloring. I used black & brown and mixed it to make it rock-like. Then we layered it with the white part. The kids wanted it marbled looking.

Rock Candy Geode with fondant

Roll it out and fit it into a small bowl. We divided ours into three small ramekin dishes. We lined them with foil first, then pressed in the pieces of fondant. This forms the outer rock part.

Candy Geode

For the crystalized part, you just make a sugar water solution. We used 1 c. of water and 2 c. white sugar. Cook it in a small pot until the sugar is completely dissolved. Add in any coloring you would like to use. If you are doing different colors, divide them out first. Pour the sugar water into the hollow of the rock part.

Making candy geodes

 

Wrap the entire bowl in foil and seal it up. Let it set for about 3 days. The sugar will crystalize. You can open it and peek, but watch out for spilling! It get’s messy. (experience)  After a couple of days, pour out the extra liquid and let it dry opened.

Rock Candy Geode

 

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Want more geology education ideas? Check out my Identify Rocks With Kids post.  It has a fun printable!

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Want more edible education ideas?  I have a post with 100 of them!

STEAM for Kids

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5 Comments

  1. I used to use a range of edible projects to teach some geology – very popular for the boys I taught to do at home or in class.
    1) Sedimentary rocks -just wet some coloured sugar enough to get it to stick like wet sand. Mold in a cup or little cake mold and tip out to dry over night. Instant sedimentary rock, just the way it really forms in nature, just a few million years faster.
    2) basalt vs rhyolite lava – cook up some golden syrup as for hokey pokey candy
    100 grams caster sugar
    4 tablespoons golden syrup
    1 ½ teaspoons bicarbonate of soda via Nigella Lawson
    slowly bring to a boil. Pour out a little bit on greased foil – runs like basalt lava.
    add baking soda and pour out immediately – stiff and foamy like rhyolite
    3) heat circulation inside the earth – bring a small pot of water to the boil. Throw in a handful of uncooked rice or macaroni. Observe the way the rice/pasta moves up, around, then down, like the circulation that moves the tectonic plates over the earth.
    4) metamorphic rocks transformed by heat – any good cookie recipe for molded cookies or ones you can press a pattern into. If you layer vanilla and chocolate dough, you can apply a little pressure from the side or use the tines of a fork to form anticline and syncline forms.
    5) fossil casts – sugar as for sedimentary rocks, put into a patty and then a shape pushed in to make the cast. Let dry and eat!

  2. Interesting experiments – fun. I wonder if there is a way to teach health with them in addition. I cringed when I saw shortening as an ingredient – hoping the kids weren’t eating trans fats. I guess calcium alginate in the froodles is an OK food. Very creative lessons. The kids must love your classes.

  3. Awesome! I teach once a week so I would have to take them home and bring them back the following week for the kids. Do you think they would hold-up that long? Thanks!

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