sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs). Color: Tan, brown, orange, and red hues. Luster: Waxy to vitreous (glassy) on broken surfaces. Crystal structure: Cryptocrystalline/microcrystalline quartz. Cleavage: None, exhibits conchoidal fracture. Specific gravity: 2.6-2.9.

Hardness: 6
Color: Tan, brown, orange, and red hues
Luster: Waxy to vitreous (glassy) on broken surfaces

Identified June 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (primarily silica) over millions of years after being buried by sediment or volcanic ash. Common examples range from the Carboniferous to the Pliocene epochs.

Uses & applications

Used widely in decorative lapidary arts, jewelry (cabochons), interior design (tables, bookends), and as a popular teaching and collection specimen.

Geological facts

The wood structure is often preserved in such high detail that tree rings and cellular structures can be studied under a microscope. The Petrified Forest National Park in Arizona is one of the most famous sites in the world for these specimens.

Field identification & locations

Identify by looking for bark textures and growth ring patterns combined with the weight and hardness of stone. It is commonly found in gravel pits, riverbeds, and areas with ancient volcanic ash falls. Collectors should check local laws as collecting on federal land is often restricted.