sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, varied colors including brown, yellow, red, and black, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz/chalcedony), conchoidal fracture, specific gravity around 2.5 to 2.7.

Identified July 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in fine, oxygen-poor, mineral-rich sediments such as volcanic ash or river mud, preventing decay. Over millions of years, groundwater rich in dissolved silica percolates through the wood, replacing organic cellular structure with quartz or chalcedony.

Uses & applications

Used for ornamental objects, decorative bookends, lapidary art, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood can preserve the microscopic cellular structure of ancient trees dating back hundreds of millions of years, sometimes as far back as the Carboniferous period.

Field identification & locations

Identified by its retention of tree rings, bark texture, and wood grain combined with the extreme hardness and weight of stone. Found worldwide, with famous deposits in Arizona's Petrified Forest National Park.