In the natural world, fossils that aren't actually fossils are known as concretions. These occur naturally when mineral deposits, such as siderite or limestone, infiltrate rock formations. Many amateur collectors make the mistake of believing a concretion to be a dinosaur egg or an ancient turtle shell fossil. However, there are other reasons that a fossil can look exactly like the real thing when it isn't. It's when you cast--or even make--a fossil yourself.
Make a Fossil
Make a cast or mold of a fossil that is in your existing collection or one from a purchased collection. Some good fossil specimens for this type of project include mollusks, bone, petrified wood and rocks.
Get the supplies and directions needed to make a fossil cast from a hobby supply store, or get the materials and simple instructions provided online by Home Science Tools (see Resources below).
Use the super easy way to make a fossil cast. Simply shape some heavy-duty aluminum foil so that it forms a bowl, with the center area being flat and smooth and the surrounding walls secure from leakage.
Pour a small amount of prepared plaster of paris in the center of the aluminum bowl.
Insert a shell or other small object into the plaster and let the mixture harden for 30 minutes.
Remove the aluminum foil to reveal your fossil.
Make a mold of a real fossil that rivals any museum specimen. The Create-A-Fossil kits offered by Amtraco include all necessary materials and are pre-molded to replicate Pterodactylus kochi, Kueichousaurus hui or a Massospondylus skull (see Resources below).