fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs); Color: Dark gray, brown, black; Luster: Dull to vitreous; Crystal Structure: Microcrystalline (Quartz/Chalcedony); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Dark gray, brown, black
Luster: Dull to vitreous

Identified July 17, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Dark gray, brown, black; Luster: Dull to vitreous; Crystal Structure: Microcrystalline (Quartz/Chalcedony); Specific Gravity: 2.6-2.9

Formation & geological history

Formed when organic plant material is buried by sediment and replaced by minerals (usually silica) via permineralization, typically over millions of years starting in the Paleozoic era.

Uses & applications

Used for decorative items, lapidary work, jewelry, aquarium decor, and as educational fossil specimens.

Geological facts

It is the state gem of Washington and the state fossil of Arizona. The organic structure such as tree rings and cellular bark patterns can often be preserved in incredible detail.

Field identification & locations

Identify by looking for wood-like grain, bark textures, or growth rings in a heavy, stony material that cannot be scratched by a steel knife. Common in Arizona, Oregon, and Madagascar.