Fossil Making Projects

Rock Fossils

• Fossils are often found in soft rock such as limestone and shale, which wears away more easily than other types of rock. As the rock erodes, the fossils within are revealed. Making fossil casts demonstrates how fossils are made. Place about one inch of clay into a small foam bowl. Press a toy animal, a coin, or a rock into the clay to leave a clear imprint. Mix a half cup of plaster of Paris with water until it is smooth and thick, and pour it into the can or bowl over top of the clay. Fill the bowl to a depth of about one inch. Leave the plaster to dry for about 24 hours then remove it from the bowl. Remove any bits of clay and examine your fossil. Experiment with different objects to determine which will make a better fossil then paint your fossils to resemble rocks.

Fossils in Mud

• Simulate fossils that form in the mud on the ocean bottom. Find a leaf that is not dry or crumbly. Mix about a half cup plaster of Paris with water until it is slightly thicker than pancake batter. Spread the plaster onto a piece of cardboard until it is about an inch in thickness and just larger than your leaf. Coat your leaf in petroleum jelly and press it down into the plaster. Leave it to dry. When dry, remove the leaf and look at your fossil. Repeat the process with various shells.

Fossilized Patterns

• Fossils can leave intricate patterns in materials such as rock and tree sap. Paleontologists use these fossils to study what life might have been like millions of years ago. Make fossils out of plasticine to simulate the details fossils can contain. Flatten a ball of plasticine to a thickness of about an inch. Smooth the surface. Place the plasticine into a paper cup with the smooth side facing up. Press an object with an intricate pattern such as a coin or a shell into the plasticine. Remove the object and examine the impression left behind. Pour a half cup of plaster of Paris into another paper cup and mix with water until smooth, like pancake batter. Let it stand for about two minutes then pour into the cup with the impression. Leave about 24 hours and when dried, tear the sides of the cup away to remove your fossil. Examine the fossil and compare with your object to determine how many details transferred to the fossil imprint.

Sandbox Fossils

• Younger scientists can make fossils in a sandbox. Fill two small buckets with damp sand. Find some toys or objects with detailed shapes such as small plastic dinosaurs, branches or shells. Press each object into the sand in the buckets. Remove it and check that the impression is clean. Mix plaster of Paris according to package directions. Pour the mixture over the sand impressions and leave to dry. Remove the plaster when dry and use a soft brush to remove the sand.