fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 7 on the Mohs scale. Colors range from brown, tan, and yellow to red, green, and black depending on mineral impurities. Luster: Vitreous to dull. Crystal structure: Microcrystalline quartz (chalcedony/jasper). Cleavage: None (fractures conchoidally). Specific gravity: 2.5 - 2.7.

Hardness: 7 on the Mohs scale
Luster: Vitreous to dull

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-free environment (such as a mudslide or volcanic ash) and groundwater rich in dissolved minerals (mostly silica) permeates the wood, gradually replacing the organic cells with stone over millions of years.

Uses & applications

Used in ornamental carvings, lapidary arts, jewelry, high-end home decor, and by fossil and rock collectors.

Geological facts

Petrified wood retains the original cellular structure of the ancient tree, sometimes down to individual growth rings, allowing scientists to study prehistoric forest ecosystems.

Field identification & locations

Look for wood-like textures, bark patterns, or grain lines coupled with a high density and the ability to scratch glass (hardness of 7). Commonly found in regions with ancient volcanic activity and river sediment deposits like Arizona, USA (Petrified Forest National Park) and Madagascar.