Discuss why the children selected a particular rock. Write children's exact words on large chart paper. Compare the rules that were selected by the class to the rules in the book. Discuss the rules that the class added or left out. This activity will provide children with an understanding of how rules are made.
Children can compare and categorize their rocks according to color, weight, size, texture, etc.
Encourage children to predict which is the biggest rock, the heaviest, etc. If possible, use rocks that will pose contradictions to the children. For example, bring in a large rock that weighs less than a more dense small rock. Use different kinds of scales to weigh the rocks. Make a chart or use graph paper for the children to record how many cubes their rock weighed.