sedimentary

Petrified Wood

Silicified Wood (primarily SiO₂)

Hardness: 6.5–7 on Mohs scale. Color: Tan, cream, and brown (iron/manganese inclusions). Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline (chalcedony/quartz). Cleavage: None (conchoidal fracture). Specific gravity: 2.6–2.9.

Hardness: 6
Color: Tan, cream, and brown (iron/manganese inclusions)
Luster: Vitreous to waxy

Identified March 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization, where organic wood material is replaced by silica-rich water in anaerobic conditions. Typically found in deposits from the Triassic through the Cenozoic eras (approx. 20 to 200 million years old).

Uses & applications

Used for ornamental carvings, jewelry (cabochons), furniture (slices for tabletops), and as geological display specimens for private collectors.

Geological facts

In some specimens, the replacement is so perfect that microscopic cell structures and tree rings are preserved. The Arizona Petrified Forest is the most famous location globally for these specimens.

Field identification & locations

Identify by looking for bark textures and wood grain patterns on a stone that is much harder and heavier than regular wood (will not scratch with a pocketknife). Commonly found in dry basins and riverbeds in Arizona, Oregon, and Madagascar.

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