Rock Identifier
Fossilized wood (petrified wood) (Silicified fossil wood; commonly quartz/chalcedony (SiO₂) replacing wood) — fossil
fossil

Fossilized wood (petrified wood)

Silicified fossil wood; commonly quartz/chalcedony (SiO₂) replacing wood

AI-generated identification · may be incorrect

Typically dark brown to black with preserved linear wood grain; dull to slightly waxy or glassy luster, hardness about 6.5–7 Mohs, no cleavage, and specific gravity roughly 2.3–2.7. The visible parallel texture and irregular growth-like patterns are consistent with wood anatomy rather than ordinary rock banding.

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Physical properties

Typically dark brown to black with preserved linear wood grain; dull to slightly waxy or glassy luster, hardness about 6.5–7 Mohs, no cleavage, and specific gravity roughly 2.3–2.7. The visible parallel texture and irregular growth-like patterns are consistent with wood anatomy rather than ordinary rock banding.

Formation & geological history

Buried wood was gradually mineralized as silica-rich groundwater replaced cellular material, often during volcanic or sedimentary burial. Petrified wood ranges from Paleozoic to Cenozoic in age, commonly tens to hundreds of millions of years old.

Uses & applications

Used as a cabinet, carving, lapidary, and display material; polished pieces are popular collectibles, though this specimen appears rough and unpolished.

Geological facts

Silicification can preserve microscopic cell structure so precisely that tree species may sometimes be identified. Iron, manganese, or carbon impurities produce brown, black, red, and yellow colors.

Field identification & locations

Look for consistent wood grain, growth rings, knots, and a stone-like weight; a steel file should not easily scratch it if quartz-rich. Common localities include Arizona, Oregon, Indonesia, Madagascar, and Argentina.

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