fossil

Petrified Wood

Silicified wood (Quartz / Chalcedony replacement)

Hardness: 6.5 to 7 on the Mohs scale; Color: Brown, tan, grey, white, and occasionally red or blue depending on mineral impurities; Luster: Vitreous to waxy; Crystal structure: Microcrystalline quartz (chalcedony); Cleavage: None (conchoidal fracture); Specific gravity: 2.5 to 2.7

Hardness: 6
Luster: Vitreous to waxy

Identified August 1, 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 ancient trees were rapidly buried by sediment, volcanic ash, or mud, cutting off oxygen and preventing decay. Mineral-rich groundwater flowing through the sediments slowly dissolved the organic wood tissues and replaced them atom-by-atom with silica (quartz, opal, or chalcedony). Dates range from millions to hundreds of millions of years old.

Uses & applications

Used for ornamental carvings, polished display slabs, bookends, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood retains the original cellular structure of the tree, sometimes even preserving annual growth rings and bark details down to the microscopic level. The Petrified Forest National Park in Arizona contains one of the world's largest and most colorful concentrations of petrified wood.

Field identification & locations

Can be identified in the field by its distinct wood-like exterior texture and grain patterns combined with an unexpectedly heavy weight and stone-like hardness that will easily scratch glass. Common locations include the western United States, Argentina, and various deserts worldwide.

Other fossil specimens

See all

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil

Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

sedimentary

Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

sedimentary

Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

fossil

Fossiliferous Limestone

Limestone with embedded fossil cross-section

sedimentary

Fossiliferous Limestone with Crinoid stems

Limestone (CaCO3) containing Crinoidea fossils

sedimentary