sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 (Mohs scale); Color: tan, brown, beige with some gray; Luster: vitreous to dull; Crystal structure: cryptocrystalline (chalcedony/quartz); no cleavage; specific gravity approx. 2.6.

Hardness: 6
Color: tan, brown, beige with some gray
Luster: vitreous to dull

Identified March 20, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 (Mohs scale); Color: tan, brown, beige with some gray; Luster: vitreous to dull; Crystal structure: cryptocrystalline (chalcedony/quartz); no cleavage; specific gravity approx. 2.6.

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (usually silica) from groundwater while buried under sediment or volcanic ash. This process typically takes millions of years, often dating back to the Triassic or Jurassic periods.

Uses & applications

Used for ornamental jewelry (cabochons), interior decoration (furniture, bookends), and highly sought after by geological collectors for its preservation of biological structures.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. The cell structure of the original tree is often so perfectly preserved that the species of tree can be identified by paleontologists.

Field identification & locations

Identify in the field by looking for 'fossilized' bark patterns and wood grain textures on the surface of heavy, rock-like fragments. Commonly found in arid regions like Arizona, Utah, and parts of the Pacific Northwest.