fossil

Petrified Wood

Fossilized plant material (Silicon dioxide - SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Brown, black, gray, Luster: Dull to waxy, Crystal structure: Microcrystalline (chalcedony) replacing organic structure, Fracture: Conchoidal

Hardness: 6

Identified July 28, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: Brown, black, gray, Luster: Dull to waxy, Crystal structure: Microcrystalline (chalcedony) replacing organic structure, Fracture: Conchoidal

Formation & geological history

Formed when plant material is buried by sediment and protected from decay. Groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, pyrite, or another inorganic material such as opal. Can be millions of years old.

Uses & applications

Used in jewelry, decorative items, bookends, tabletops, and collected by rockhounds.

Geological facts

The petrified wood retains the original structure of the wood, right down to the microscopic level, often showing tree rings. The Petrified Forest National Park in Arizona is famous for its large logs of petrified wood.

Field identification & locations

Identified by wood-like appearance combined with stone-like hardness and weight. Commonly found in areas with ancient volcanic activity or ancient riverbeds.

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