Rock Types





Name of Activity

Rock Types


Emily Cerveira


1 Hour Total, demo, rock, sedimentary, igneous, metamorphic



Grade Level



1 Hour Total

Brief Description

Students will watch three demos that show how each main type of rock is formed (sedimentary, igneous, and metamorphic).

Lesson Objectives:

To classify and distinguish between three main types of rocks.

Materials Needed:


Epsom salt



Waxed paper

Heavy books



rice krispies

chocolate chips/M&Ms



Necessary Background

There are three different types of rocks: sedimentary, igneous, metamorphic. Sedimentary rock is formed out of soil, silt, sand, seashells, and other pieces. The tiny bits settle and build up in thick layers. Minerals from water seep into the spaces between the particles and bond them into solid rock. The Grand Canyon is made up of sandstone, limestone, and shale which are all sedimentary rocks. Igneous rock was once hot liquid inside the earth. Rock that erupted from volcanoes and cooled on the surface is called extrusive igneous rock. Igneous rock that cooled more slowly inside the Earth is called intrusive. Apache Tear and the Hawaiian Islands are mainly igneous rock. Metamorphic rock is igneous or sedimentary rock that is changed by heat, pressure or both. The Appalachian Mountains including the Blue Ridge are mainly metamorphic rock with a little igneous rock.






  1. Begin with a class discussion on types of rocks, how they were formed, and how they are related to each other.
  2. Sedimentary Rock Demo:
    1. Mix 1 cup of water and 1/2 cup of Epsom salt in a mixing bowl. Stir until most of the salt dissolves. Place about 1 inch of sand in a small paper cup. Add enough salt solution to just cover the sand. Mix well. Let the mixture stand until dry (about 2 – 3 days). Cut off the paper. Take a close look a the rock. Where is the salt? How does it hold the sand together. (you may want to have an example prepared ahead of time)

  • Metamorphic rock demo:
    1. Make about 2 – dozen pea-sized balls from clay of different colors to represent rock particles. Place the clay balls close together on apiece of waxed paper. Place a second sheet of waxed paper on top of the clay balls. Stack some books on top of the waxed paper. Imagine that the books are layers of rock building on top of the rock particles. The pressure of the rock particles increases as you add each book. Heat builds as the rock particles are pushed deeper into the Earth’s crust. Now remove the books an peel away the waxed paper. An entirely new type of rock has been formed.

  • Igneous rock demo:
    1. Place the marshmallows and butter in a pan. Stir and melt. Add the rice krispies. Stir. Place a cup of the warm rice krispies mixture on the waxed paper square. Sprinkle and roll into the mixture other ingredients like raisins, chocolate chips, M&Ms with your hands. These ingredients will form the rock surface. After it cools and hardens you have created an edible igneous rock!

    Reference 1

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