Organic & Fossils
Fossil
What it is
Preserved remains of ancient organisms, mineralized over millions of years. Ammonites are extinct cephalopods whose coiled shells were replaced by calcite or pyrite. Orthoceras are straight-shelled nautiloids from 400+ million years ago.
How it forms
Fossilization occurs when an organism is rapidly buried in sediment, and mineral-rich water gradually replaces the original organic material with stone — molecule by molecule, over millions of years.
CaCO₃, SiO₂, or FeS₂ (replacement minerals)
