fossil

Petrified Wood

Fossilized wood, permineralized wood (typically composed of SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7.5 (Mohs), Color: varies widely (brown, grey, tan, white in this specimen), Luster: dull to waxy (glassy when polished or wet), Crystal structure: cryptocrystalline (chalcedony/opal replacement), Cleavage: none, Specific gravity: 2.58-2.91

Hardness: 6

Identified August 25, 2026More fossil →

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Physical properties

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. This process can take millions of years.

Uses & applications

Used in lapidary arts for cabochons, beads, and carvings. Larger pieces are used for bookends, tabletops, and display specimens. Highly valued by collectors and natural history enthusiasts.

Geological facts

Petrified wood is the state fossil of several US states, including Washington and North Dakota. The Petrified Forest National Park in Arizona is famous for its large, brightly colored logs.

Field identification & locations

Identified by the preservation of original tree structures like tree rings, bark, and cellular wood grain, combined with the hardness and weight of stone. Often found in ancient riverbeds, volcanic ash deposits, and sedimentary rock formations.