fossil

Petrified Wood

Silicified Wood (primarily quartz/chalcedony replacing organic wood structure)

Hardness: 7 on the Mohs scale; Color: Varies widely including brown, white, red, yellow, and black depending on mineral impurities; Luster: Vitreous to waxy; Crystal structure: Microcrystalline quartz (chalcedony); Cleavage: None (conchoidal fracture); Specific gravity: 2.5 - 2.7

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

Identified August 7, 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 in sediment low in oxygen, preventing decay. Groundwater rich in dissolved silica slowly percolated through the wood, replacing organic matter cell-by-cell with minerals like quartz or opal over millions of years.

Uses & applications

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

Geological facts

Petrified wood can preserve the fine cellular structure of the original tree down to microscopic detail. Famous locations include the Petrified Forest National Park in Arizona.

Field identification & locations

Can be identified in the field by its wood-like external grain texture combined with an unusually heavy weight and a hard, glassy, conchoidal fracture typical of quartz.

Other fossil specimens

See all

Crinoid Stem Fossil in Matrix

Phylum Echinodermata, Class Crinoidea

fossil

Chert with Fossil Brachiopod

Microcrystalline Quartz (SiO2) with Calcitic Brachiopod inclusion

sedimentary

Sedimentary Outcrop (Sandstone/Shale)

Sedimentary bedrock formation (variable composition)

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