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Crush summer science with these yummy sedimentary rock cookies

August 12, 2019 2 min read

One of our favorite peeps from Sassafras Science, Summer Beach, loves to finish off a good sandwich-lunch with a cookie for dessert and these sedimentary rock cookies are a perfectly yummy way to blend science and food during the summer!

Crush summer science with these yummy sedimentary rock cookies

Before we share the recipe for the rock cookies, let's review a bit about sedimentary rocks.

Sedimentary Rock Science

Rocks are the hard objects that make up the Earth's surface. We can literally find them everywhere! 

Rocks can be broken into three main categories based on how they were formed. There are igneous, metamorphic, and sedimentary rocks.

Sedimentary rocks are made from various layers of crushed minerals and the decayed remains of plants or animals. The layers can easily be seen and sedimentary rock tends to be very weak.

These rocks make up about 75% of the Earth's surface! Sandstone, limestone, coal, and gypsum are all examples of sedimentary rocks.

So now that we know what these rocks are, let's get to the yummy science!

Sedimentary Rock Cookie Recipe

These sedimentary rock cookies are made layer by layer, just like sedimentary rocks. You will need the following ingredients:

  • 1/2 cup butter 
  • 1 and 1/2 cups graham cracker crumbs
  • 1 (14 oz.) can sweetened condensed milk
  • 1 cup of chocolate chips
  • 1 cup of peanut butter chips
  • 1 cup chopped nuts

Here's how to make the cookies:

  1. Preheat the oven to 350 degrees and use this heat to melt the butter in a 9” by 13” baking pan.
  2. Sprinkle the graham cracker crumbs over the butter. (If you want, you can use whole graham crackers when making these.)
  3. Next, spread the chocolate chips over the crumbs, followed by the nuts and then the peanut butter chips.
  4. Then, press down gently and pour the condensed milk evenly on top.
  5. Bake the cookies for 25-30 minutes at 350 degrees. 

Let the cookies cool a bit before cutting them into squares. After they cool completely, you can eat and enjoy your sedimentary rock treats!

Wrapping it up

Want to learn more about rocks, here are a few ways we can help with that:

4 Responses

Cindy McPhail
Cindy McPhail

September 18, 2019

I read all the comments about them being too sweet and decided to add a layer of chopped pretzels to the top. It added a salty and crunchy component. They were definitely still sweet, but to me they weren’t TOO sweet…my kids loved them!

Mary Abele
Mary Abele

September 03, 2019

To reduce the sweetness, I wonder if regular condensed milk might work as well

Paige Hudson
Paige Hudson

September 02, 2019

Elizabeth, they are pretty sweet! You could try replacing the chocolate and peanut butter chips with different types of nuts, but it won’t be exactly the same effect. If you don’t want a sweet treat, you can use crayon shavings to show the rock cycle instead :-).

Elizabeth Morrill
Elizabeth Morrill

September 02, 2019

We made these a few weeks ago as part of our pre-k homeschool! While they were easy to make, they are SUPER sweet. Like, instant-diabetes-sweet. I wonder if there’s a way to make these slightly less decadent? Even my sweets-loving four-year-old could only take a few bites before it was just too much.

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