sedimentary

Petrified Wood

Silicified wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, variable colors including brown, grey, red, and yellow, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz/chalcedony), conchoidal fracture with no true cleavage, specific gravity around 2.5 to 2.7.

Identified July 28, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in low-oxygen, mineral-rich sediment like volcanic ash or flood plains. Over millions of years, groundwater rich in dissolved silica replaces the organic wood cell walls with quartz, chalcedony, or opal while preserving the original cellular structure.

Uses & applications

Used in ornamental stone carving, lapidary arts, jewelry making, bookends, tabletops, and as sought-after specimens for fossil and mineral collectors.

Geological facts

Petrified wood can preserve microscopic cellular details of ancient flora dating back hundreds of millions of years, with some of the most famous deposits located in the Petrified Forest National Park in Arizona.

Field identification & locations

Can be identified in the field by its distinct wood-like grain, bark texture, and weight, coupled with the cold, hard feel and conchoidal fracture of stone. Found worldwide in sedimentary strata associated with ancient forests and volcanic activity.