My apologies, we are behind again with our parasha work. Here is an interesting extension activity to be done with Parashat Vayeitzei. Rocks seem to be a focal point in last week's parasha. Yaakov rests his head on rocks before he the dream of the ladder and rocks are used in the pact made between Yaakov and Laban.
So here are some preschool Earth science activities all about rocks I found on teachpreschoolscience.com: