fossil

Petrified Wood

Silicified wood (primarily quartz, SiO2)

Hardness: 6.5 to 7 on the Mohs scale; Color: Varies widely including brown, tan, black, grey, red, and yellow due to mineral impurities; Luster: Vitreous to waxy when polished, dull to earthy on raw surfaces; Crystal structure: Microcrystalline quartz (chalcedony/jasper); Cleavage: None (conchoidal fracture);…

Hardness: 6

Identified July 31, 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 through permineralization, where organic wood material is buried under sediment in anoxic conditions and gradually replaced by groundwater-borne minerals (usually silica) over millions of years, often dating from the Triassic period or older.

Uses & applications

Used in decorative items, lapidary arts, jewelry, bookends, tabletops, and as collector specimens.

Geological facts

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

Field identification & locations

Can be identified in the field by its distinct wood-like grain, bark texture, and high density/hardness compared to actual wood. Found worldwide, with famous deposits in Arizona's Petrified Forest National Park, Argentina, and Madagascar.

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