Place the objects in a paper bag. Give each student a lump of clay and a plastic bag. Let each student choose an object from the paper bag, without showing it to the others. Have them put their clay in the plastic bag and flatten it. Students press objects into clay through the bag.
Students remove clay from the bag.
The minerals harden into stone. The stone is shaped like the original living creature. A one-fourth teaspoon of salt speeds hardening. Distribute milk cartons and spoons and have students wipe clay imprints lightly with oil. Kids place imprints into milk cartons and, using spoons, cover them with about an inch of plaster of paris.