sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: typically browns, grays, and tans (can show reds/blues depending on trace minerals); Luster: vitreous to waxy; Crystal structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None

Hardness: 6
Luster: vitreous to waxy

Identified February 24, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) in an anaerobic environment. This process typically occurs over millions of years, often in volcanic ash beds or river sediments; ages range from the Devonian to the Pleistocene.

Uses & applications

Used in decorative art, high-end furniture (slabs), jewelry (cabochons), and as a popular specimen for geological and fossil collecting.

Geological facts

Despite being made of stone, the specimen often retains the original cellular structure of the wood, including bark patterns and growth rings. Arizona's Petrified Forest National Park contains one of the world's largest concentrations of this material.

Field identification & locations

Identify in the field by looking for a 'woody' texture or bark-like exterior on a heavy, dense rock that cannot be scratched by a steel knife. Common in areas with ancient volcanic activity and sedimentary basins like the American Southwest and Madagascar.