fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 7 on the Mohs scale. Color: Varies widely including white, grey, brown, red, and yellow depending on mineral impurities. Luster: Vitreous to waxy when polished. Crystal structure: Microcrystalline quartz (chalcedony/jasper). Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.5 to 2.7.

Hardness: 7 on the Mohs scale
Luster: Vitreous to waxy when polished

Identified July 28, 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 fallen trees are rapidly buried in low-oxygen, mineral-rich sediment, typically volcanic ash or flood plains, preventing decay. Over millions of years, groundwater rich in dissolved silica replaces the organic wood cell walls with quartz, preserving the original structural details.

Uses & applications

Used for ornamental carvings, high-end lapidary work, jewelry, decorative tabletops, and as prized collector specimens.

Geological facts

Some petrified wood specimens retain such fine cellular preservation that paleobotanists can identify ancient tree species down to the microscopic level. Arizona's Petrified Forest National Park contains one of the world's largest and most colorful concentrations of petrified wood dating back to the Triassic period, roughly 225 million years ago.

Field identification & locations

Can be identified in the field by its distinct tree bark texture or growth rings coupled with an unusually heavy weight and cold-to-the-touch rock feel. Commonly found in sedimentary layers associated with ancient riverbeds and volcanic regions worldwide.