fossil

Petrified Wood

Silicified Wood (primarily Quartz/Chalcedony, SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, gray, and black; Luster: Dull to waxy; Crystal structure: Cryptocrystalline (replacing organic cellular structure); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, gray, and black
Luster: Dull to waxy

Identified July 15, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood material is replaced by minerals (usually silica) over millions of years. This specimen likely dates from the Paleozoic to Cenozoic eras, formed in anaerobic conditions under volcanic ash or sedimentary layers.

Uses & applications

Used for decorative ornaments, bookends, jewelry (cabochons), landscaping, and as educational geological specimens.

Geological facts

Petrified wood is the state fossil of several US states including Arizona and Washington. The process is so precise that individual tree rings and even cellular structures can often be seen under a microscope.

Field identification & locations

Identify by looking for bark textures, wood grain, or growth rings on a stone that is much heavier than wood and cannot be scratched by a steel knife. Commonly found in areas with historical volcanic activity or ancient river basins like the Petrified Forest National Park.

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