Petrified Wood

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Variegated brown, tan, red, grey; Luster: Vitreous to waxy; Structure: Cryptocrystalline; Specific Gravity: 2.6-2.9

Formation & Geological History

Formed through permineralization when plant material is buried by sediment or volcanic ash and replaced by silica-rich groundwater. Most specimens date from the Devonian to the Tertiary periods (millions of years ago).

Uses & Applications

Used for ornamental furniture, lapidary items, jewelry (cabochons), interior design, and as a popular collector's specimen.

Geological Facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. In some cases, the replacement is so perfect that the microscopic cellular structure of the original tree is preserved.

Field Identification & Locations

Identify by looking for preserved growth rings, bark texture, or woody grain in a stone that is much harder than wood. Frequently found in the American Southwest, Oregon, and Washington.

Identified on: 5/10/2026

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