mineral

Petrified Wood

Silicified Wood (primarily Quartz/Chalcedony, formula SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, gray, sometimes reddish; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, gray, sometimes reddish
Luster: Dull to waxy

Identified May 10, 2026More mineral →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, gray, sometimes reddish; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) from groundwater while keeping the original cellular structure. Ages range from the Devonian to the Pleistocene.

Uses & applications

Used for jewelry (cabochons), interior decoration (tabletops, bookends), and highly valued by fossil collectors and educational institutions.

Geological facts

Petrified wood is the state fossil of several US states, including Arizona and Washington. The largest collection is found in the Petrified Forest National Park in Arizona.

Field identification & locations

Identify in the field by looking for wood-like grain patterns, growth rings, or bark textures on a stone that is too hard to be scratched by a steel knife. Commonly found in sedimentary deposits.