fossil

Petrified Wood

Silicified wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, colors range from brown, tan, and yellow to red and black depending on mineral impurities, vitreous to waxy luster, amorphous crystal structure (quartz/chalcedony replacement), conchoidal fracture.

Identified August 2, 2026More fossil →

Explore Petrified Wood in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed when organic plant material is buried in an oxygen-depleted environment (such as volcanic ash or sedimentary mud) and groundwater rich in dissolved silica replaces the original cell walls mineral by mineral over millions of years.

Uses & applications

Used for ornamental carvings, polished display specimens, jewelry, lapidary art, and sought after by fossil and mineral collectors.

Geological facts

Some petrified wood logs can preserve microscopic cellular structure of ancient trees dating back over 200 million years to the Triassic period.

Field identification & locations

Identified by retaining the exterior texture and growth rings of wood while feeling exceptionally heavy and having the hard, glassy texture of quartz. Found worldwide, famously in Arizona's Petrified Forest National Park.