sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7.0 (Mohs); Color: Tan, brown, gray, and black banding; Luster: Waxy to vitreous; Structure: Microcrystalline (preserving cellular structure); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Tan, brown, gray, and black banding
Luster: Waxy to vitreous

Identified June 19, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic environments such as volcanic ash or fluvial sediments, often dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used for making lapidary items, bookends, jewelry, furniture (tabletops), and highly valued as decorative mantel pieces and museum specimens.

Geological facts

Unlike most fossils, petrified wood is a three-dimensional representation of the original organic material; in some cases, the original cellular structure can be observed under a microscope. Arizona's Petrified Forest National Park is one of the most famous sites for these specimens.

Field identification & locations

Identify by looking for wood-like grain patterns, bark textures, and annular rings in a heavy, cold-to-the-touch stony material. Commonly found in areas with historical volcanic activity and sedimentary basins.