fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, cream, and grey with some blue-grey quartz; Luster: Vitreous to waxy; Texture: Retains original woody grain structure; Cleavage: None (conchoidal fracture)

Hardness: 6
Color: Brown, tan, cream, and grey with some blue-grey quartz
Luster: Vitreous to waxy

Identified July 18, 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 via permineralization where organic wood materials are replaced by silica (quartz) from groundwater over millions of years, often in volcanic or sedimentary environments.

Uses & applications

Used for decorative items, jewelry (cabochons), lapidary art, and as a popular specimen for fossil collectors.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona and Louisiana. It can preserve even the smallest microscopic cellular details of the original tree.

Field identification & locations

Identify by looking for wood-like growth rings, bark textures, or grain patterns in a stone that can scratch glass. Often found in riverbeds or areas with high volcanic ash deposits.