pre-heat the oven to put broken crayon pieces in a mini cupcake mold (either use paper cups or spray mold with vegetable oil). "cook" mold for about 10 minutes; they melt very fast. remove from the oven and let cool completely.
Color rocks with crayons. Place the rocks on a foil lined cookie sheet and bake them for 15 minutes at 200 degrees to melt the crayons. Let them cool and then grab an old sock, turn it inside out and rub the rock to polish it up and make it shine.