Friday, January 27, 2012

Crayon Rocks

We've had a very, very warm winter here in Michigan.  With such little snow, the ground has been exposed and my little rock hounds have been collecting rocks again.  I thought we'd revisit the types of rocks again (sedimentary, metamorphic and igneous) - but this time give them a more active and visual way to think about how each are formed.  There are many examples of creating rocks from crayons, but this pdf from the the Exploratorium is very helpful.

Materials Needed:
  • crayons, several of each in four different colors
  • crayon or pencil sharpener
  • 4 containers for holding the crayon shavings
  • 3-6"x6" pieces of aluminum foil
  • popsicle stick or other disposable stirrer
  • mug
  • boiling water

Unwrap the crayons and use the sharpener to create shavings.  You can also try to make the shavings use a penny or a plastic knife, although we found that the sharpener was easier and more productive than the penny or knife especially for the little ones.  Make sure to keep the shavings separate from each other at this point.

Sedimentary rocks
Sedimentary rocks are formed from sediments (tiny rock particles that were created by weathering or erosion) that were layered and then compressed.  To replicate this with the crayon shavings, take one of the aluminum foil squares and have your child sprinkle each of the colors of shavings into the middle of the square, one at a time so they will form the layers.

Fold the aluminum foil up tightly around the shavings and then compress it.  To do this, they can press on it with their hands, step on it, place it in a clamp or use your creativity to think of other ways.  .

This does take a while to get the crayon pieces to stick together and we found that a little body heat "helps" the process along.  Carefully unfold the foil and remove the sedimentary rock with care as this is the most brittle of the rocks that you are making.
A sedimentary crayon rock.

Metamorphic rocks
Metamorphic rocks are formed when existing rocks are exposed to heat and/or pressure.  To mimic this, take another square of aluminum foil and pile all four colors of shavings in the center.  Fold up the sides of the aluminum foil to make a boat.  Pour boiling water into a mug (adult job!) and float the boat in the hot water for 15 to 20 seconds, just until the shavings have started to melt.

Quickly remove the boat and fold the foil in half so that the shavings are compressed a bit. Let it cool and solidify and then open the foil and remove the metamorphic rock.
A metamorphic crayon rock.

Igneous rocks
Igneous rocks are formed when magma (molten rock) cools and solidifies.  To make an igneous crayon rock, repeat the steps for making the metamorphic rock, except leave the the aluminum foil boat floating on the hot water for a minute or more until all the crayon sediments have melted.  (This may take more or less time depending on the brand of crayons that you have used.)  Then take the popsicle stick and stir the shavings until they are all mixed together.  Remove the boat and let the crayon cool and solidify.
An igneous crayon rock.
If you are using a science journal to record your child's experiments, then you can have them record either the process of making each type of rock or draw a picture of what they looked like at the end (or both).

What's Happening?
There are three types of rocks (sedimentary, metamorphic, and igneous) which, given the right conditions, can be changed from one into another.  This is known as the rock cycle, pictured below.

Sedimentary rocks are formed from the compaction and cementation of rock sediments and often have distinguishable layers.  They also may have fossils of organisms or other visible rock particles in them.  Metamorphic rocks are formed when existing rocks are exposed to heat and/or pressure; they often have distinct bands or blocks of crystals in them.  Igneous rocks are formed when magma cools and their characteristics, including crystal size, depends on how fast the rock cools.  If it cools quickly on the surface of the earth (extrusive igneous rocks), the crystals are small and pores may be apparent.  If it cools slowly under the earth, the crystals have a chance to grow larger.  More information of rocks can be found in our Creating a Rock Collection activity.

One thing you could try is to create intrusive vs extrusive igneous crayon rocks.  Follow the directions to make two igneous rocks, but cool one in a glass of ice and the other at room temperature.  Examine the resulting "rocks" with magnifying glasses to see if there is any difference between them.  Please let me know if you try this - this is just a brainstorm idea and I really would like to know if there are any visible differences. 

If you are looking for a good children's book describing the rock cycle, we like the book "The Rock Factory: The Story about the Rock Cycle".  It probably is best for early elementary age kids.

Finally, you could try to make the different types of rocks with chocolate.  I'm thinking white, milk and dark chocolate.  Food + science - what a yummy combination!

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  1. I love this! My kids are older, but I think I might do this with my "class" (my kids, 2 cousins, and 1 friend).

    And you could even add a step 4, and show how hardened igneous rock can be weathered to again make sedimentary rock! =)

    Found you through Pinterest. =)

  2. Oh, and I'd like to ask permission to use your Crayon Rocks image (at the top of your post) on my blog and link back to this post?
    It would be at this post:

    1. Hi Marty! This would definitely work with older kids - I've done it with middle school students and it worked great! I'd be thrilled if you linked back to this post - thanks for asking!

  3. Fabulous idea! I think my kids would love it.

  4. I've done this with different types of foods to make a type of cookie rock with choc. but this is great...they can do all the work as far a shavings ( I have 4th graders) and then use the hot water or microwave and cupcake me great ideas. I will try to cool it quickly in ice water too and see what results I get...thanks

  5. Love this! I have made edible rocks with my third graders in previous years, but this would be a good way that they could all be involved with their own crayons!!! Thanks!

  6. Actually, gneiss is a metamorphic rock. A better example of igneous rock is granite. Love this experiment though!

    1. Hey, thanks for the catch! I just saw your comment and I fixed the rock cycle picture and used granite as the example of an igneous rock instead. I had it correct on another sheet so I'm not sure what happened - I'll blame late-night delusional blogging. =)

  7. Hello! Thank you for sharing this, just in time for our rock study :)

  8. I did this with my 6th graders during student teaching a couple years back. They loved it and learned so much. Definitely a fun activity or all ages.

  9. Thank you!!! I will def do this with my second graders!!

  10. This was a dumb project for 2 year olds. Get a hobbie and a job

    1. Get a life and a dictionary, and learn to spell. Keep your ignorant comments to yourself.

    2. I am so excited!! I am going to try this with my 4th graders. I made hard purple taffy, broke it into pieces, and then stuck the pieces together and told them it was amethyst (sp). Being 4th graders, they believed me! Then, to show how igneous rock forms, I melted it in a pot and poured it into a pan. I waited for it to cool and then shaped it into a new "rock." It was the perfect lesson!! Then I applied pressure and heat from my hands to mold it into a metamorphic rock. Then, of course, I bit off a piece and they were mortified!! :)

  11. This is such a cool, cool idea. Pinning it to my Preschool Science board.

  12. Love your idea. You bring the boring science to toddlers' level in a way that is fun and easy to understand. Well done. I am going to feature your article at on Wednesday as part of Mom's Library Linky. I just started to host Mom's Library, and I found you via "30 Playful ways to teach young kids about rocks" from Mom's Library (

  13. I did this with 5th graders and they absolutely love it. What is wrong with doing it with little kids??? Bringing science to the young ones is awesome! I love it!!!

  14. This is the best hands on way of describing different types of rocks! My preschoolers will love it!! Thanks for sharing!!

  15. How long does this activity take? I am about to begin student teaching and am in the process of planning a "Rocks and MInerals" unit for first graders. This is so fun and is exactly what I want to do to teach them the different types of rocks, but I only have about 40 minutes each day for science. :(

  16. great! used it for my science fair project and i came 2nd!

  17. Great project! I am doing this tomorrow - with chocolate chips! (pink -brown -yellow)

  18. Yeah ... i also found this from Pinterest. Bookmarked this. Would surely share it with our newsletter readers at Tatvachintan

  19. Our crayons kept getting stuck in the pencil sharpener and didn't want the kids (11 & 6) so we used a potato peeler to shave the crayons! They LOVED this craft!!!!