fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 6.5-7 on the Mohs scale, colors range from brown and grey to multicolored depending on mineral impurities, vitreous to waxy luster, amorphous crystal structure (quartz/chalcedony replacement), conchoidal fracture, specific gravity around 2.5-2.7.

Identified August 3, 2026More fossil →

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Physical properties

Formation & geological history

Formed when plant material is buried in an oxygen-free environment (such as sedimentary sediment or volcanic ash) and slowly replaced by minerals dissolved in groundwater, primarily silica, over millions of years.

Uses & applications

Used for ornamental objects, jewelry, bookends, lapidary art, and valued as geological collectibles and display specimens.

Geological facts

Petrified wood retains the original cellular structure of the wood, allowing scientists to identify ancient tree species down to the cellular level. Entire forests have been preserved this way, such as in the Petrified Forest National Park in Arizona.

Field identification & locations

Can be identified in the field by its wood-like grain and exterior texture combined with an unusually heavy weight, cold touch, and glass-like hardness that cannot be scratched by a steel knife. Found worldwide in sedimentary rock layers.