fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Tan, brown, and grey; Luster: Waxy to dull; Structure: Cryptocrystalline silica replacing wood fibers; Specific gravity: 2.6-2.9.

Hardness: 6
Color: Tan, brown, and grey
Luster: Waxy to dull

Identified July 17, 2026More fossil →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Tan, brown, and grey; Luster: Waxy to dull; Structure: Cryptocrystalline silica replacing wood fibers; Specific gravity: 2.6-2.9.

Formation & geological history

Formed through permineralization where organic wood materials are replaced by silicate minerals (usually chalcedony or quartz) in anaerobic environments like volcanic ash or river sediments. Often dates from the Triassic to the Cenozoic eras.

Uses & applications

Used in lapidary work for jewelry, bookends, furniture, and as a popular collector's specimen. High-quality pieces are used for home decor.

Geological facts

Petrified wood is the state fossil of Washington, Arizona, and Mississippi. The process occurs over millions of years and can preserve cell structures and growth rings with extreme detail.

Field identification & locations

Check for woody textures, growth rings, and bark patterns. It will feel much heavier and colder than real wood and cannot be scratched by a steel blade. Common in the Western US, Madagascar, and Indonesia.