Here's how it works:
* Original material: The organism's remains (bones, wood, shells, etc.) are buried in sediment.
* Silica infiltration: Groundwater rich in dissolved silica (SiO2) seeps through the sediment.
* Replacement: The silica gradually replaces the original organic material, molecule by molecule.
* Petrified fossil: The original structure is preserved in a hardened, mineralized form.
Petrified fossils are often beautifully preserved and can provide detailed information about the organism's structure and even internal tissues.
