How Fossils Form
Burial, minerals, pressure, and time can turn ancient remains into stone-like evidence of life from long ago.
↓ Start with the fossilization stepsShort answer: fossils form when buried remains are preserved by sediment, minerals, pressure, and time.
Six steps from life to fossil
Death or tooth loss
Sharks shed thousands of teeth in their lifetime. Aside from an occasional vertebra, nothing else on a shark will fossilize.
Rapid burial
Sediment such as sand, mud, or silt covers the remains. Burial helps protect the material from oxygen, scavengers, waves, and weathering.
Layers build up
More sediment accumulates above the remains. Pressure increases and the buried layer can eventually become sedimentary rock.
Minerals move in
Groundwater carries dissolved minerals through the sediment. These minerals can fill tiny spaces or replace original material.
Fossilization happens
Through permineralization, replacement, molds, casts, or other processes, the original remains or their shape become preserved.
Erosion exposes it
Water, waves, rivers, digging, diving, or natural erosion can uncover fossils millions of years after they were buried.
Why shark teeth are common fossils
Sharks constantly lose and replace teeth throughout life. A single shark can shed 10,000-50,000 teeth in their lifetime. Enamel is much more durable than soft tissue, which gives shark teeth a better chance of being buried, mineralized, and preserved.
Teeth, shells, bones, and wood are more likely to fossilize than skin, muscle, or soft organs.
Black, gray, brown, blue, orange, green, and tan fossil colors usually come from minerals in the surrounding sediment or water.
A tooth must land in the right environment. If it is exposed, broken down, or never buried, it may never become a fossil.
Wear a real piece of ocean history
After learning how fossilization works, a real shark tooth necklace can be a meaningful gift for fossil collectors, shark lovers, kids, and ocean fans.
Common questions about how fossils form
How do fossils form?
Fossils usually form when remains or traces are buried quickly in sediment. Mineral-rich water then moves through the sediment, filling pores or replacing original material over time.
What is permineralization?
Permineralization happens when minerals carried by water fill tiny spaces inside bone, wood, teeth, or shells. The original structure may remain, but the empty spaces become mineral-filled.
What is fossil replacement?
Replacement happens when original material slowly dissolves and minerals take its place. The fossil keeps the shape or structure of the original item, but the material has changed.
How long does it take a shark tooth to fossilize?
Many collectors describe fossil shark teeth as at least 10,000 years old, and many fossil teeth are millions of years old. The exact time depends on burial, chemistry, minerals, and environment.
Why are fossil shark teeth often black?
Fossil shark teeth are often black because minerals from sediment or water entered the tooth during fossilization. Other mineral conditions can create gray, brown, blue, green, orange, or tan colors.
Why does soft tissue rarely fossilize?
Soft tissue usually decays quickly or is eaten by scavengers. Hard parts like teeth, shells, bones, and wood are more likely to survive long enough to be buried and fossilized.