Enabling cubs to learn about science by growing their own geodes. They will see crystals, salts, solutions and evaporation.
1 egg shell per cub. A bag of Epsom salts. Warm water. Food colouring. Plastic cup or container of some sort to store the geode in.
Dissolve the Epsom salts in the warm water to make a strong solution (a saturate if possible). Then add some food colouring to the solution. Put the egg shells into the plastic cups and pour the solution over the top. You need enough solution to cover the egg shell. It doesn't matter what the shell looks like, all will turn out differently. If you do it with blown eggs, you need to hold the egg under water to fill with solution.
The cubs then need to leave the egg and solution somewhere warm and uncovered so that the liquid can evaporate. They will start to see coloured crystals forming fairly quickly (a few hours if very warm and a saturated solution used). Once all the liquid has evaporated, the geode can be removed from the cup and displayed.