We get asked a lot, “How do you tell the difference between a dinosaur bone and a regular rock?” As paleontologists, we use a simple trick, The 4 S’s. Each S stands for a feature that fossilized bone will have.
Shape: Bones have very specific shapes. If you see a femur shaped rock, there is a good chance it is a fossilized femur. For small pieces, bone breaks at angles, and angular pieces should be investigated.
Shade: Fossils will be colored by the mineral that turn them to stone. Each formation will have different colored fossils. Look for colors that stand out from the surrounding rock.
Structure: Internal bone is porous, from when blood flowed through them while the animal was alive. External bone is dense and has parallel striations.
Stick: The most fun of the tests. The porous inner bone creates a vacuum seal with moisture. So by licking your thumb and pressing it to inner bone, it will stick to your thumb!
