fossil

Petrified Wood

Silicified wood (Quartz replacement of organic wood structure)

Hardness of 7 on the Mohs scale, colors range from brown, tan, and black to red and yellow depending on mineral impurities, vitreous to waxy luster, amorphous crystal structure, uneven to conchoidal fracture, specific gravity around 2.65.

Identified August 4, 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 fine-grained, oxygen-poor sediments such as volcanic ash or flood plains, preventing decay. Over millions of years, groundwater rich in dissolved silica (quartz) percolates through the wood, replacing organic material cell by cell with minerals.

Uses & applications

Used for decorative objects, ornamental carvings, jewelry, lapidary art, and sought after by fossil and rock collectors.

Geological facts

Petrified wood retains the delicate microscopic structures of the original wood, allowing scientists to identify ancient tree species that lived millions of years ago, sometimes dating back to the Triassic period over 200 million years ago.

Field identification & locations

Can be identified in the field by its distinct wood-grain texture and ring patterns combined with an unusually heavy weight and the ability to scratch glass due to its quartz composition. Found worldwide, with famous deposits in Arizona and Argentina.

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

Crinoid Stem Fossils (Indian Beads / St. Cuthbert's Beads)

Crinoid columnal ossicles (phylum Echinodermata)

fossil

Fossilized Crinoid Stem in Limestone

Crinoidea (Class) in Calcium Carbonate (CaCO3) matrix

fossil

Fossiliferous Limestone

Limestone with embedded fossil cross-section

sedimentary