Cool science experiment all in an eggshell! Here is an experiment to introduce the scientific method and create egg geodes. Compare the reactions of sea salt, borax and kosher salt using color to bring out the captivating results of this science experiment.

source: tinkerlab.com
Geodes in an Eggshell – Science Experiment
This multi-day science experiment uses eggs, rock and sea salt, borax baking soda and food coloring. Using clean eggshells with just the tops taken off, create solutions of the ingredients with a couple drops of food coloring. Leave the solutions poured into the shells for a few days. Observe and record the changes as your experiment continues.