fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 7 on the Mohs scale, colors range from brown, tan, and red to yellow and black, vitreous to waxy luster, amorphous crystal structure as quartz replaces organic material, no true cleavage, 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 ancient trees were rapidly buried in sediment low in oxygen, preventing decay. Over millions of years, groundwater rich in dissolved silica permeated the wood cells, replacing organic matter with chalcedony, quartz, or opal.

Uses & applications

Used for ornamental objects, lapidary art, jewelry, bookends, tabletops, and as prized specimens for fossil and mineral collectors.

Geological facts

Petrified wood can preserve cellular details of ancient plants dating back hundreds of millions of years, with famous deposits found in the Petrified Forest National Park in Arizona.

Field identification & locations

Identify by wood-like exterior texture and grain combined with a heavy, stone-like feel and vitreous fracture. Found worldwide in sedimentary rock layers associated with ancient floodplains and volcanic ash beds.