fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, gray, black with potential red/orange iron staining. Luster: Dull to waxy. Structure: Preserves original plant cell structures. Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Brown, gray, black with potential red/orange iron staining
Luster: Dull to waxy

Identified July 17, 2026More fossil →

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Physical properties

Hardness: 6.5-7 on Mohs scale. Color: Brown, gray, black with potential red/orange iron staining. Luster: Dull to waxy. Structure: Preserves original plant cell structures. Specific Gravity: 2.6-2.9.

Formation & geological history

Formed via permineralization where organic plant material is replaced by silica (usually chalcedony or quartz) over millions of years in anaerobic conditions, typically after being buried by volcanic ash or river sediment.

Uses & applications

Used for lapidary work, jewelry, interior decor (tabletops), and highly valued by fossil collectors.

Geological facts

Petrified wood is the state gemstone of Arizona. It represents a process that can take up to 100 million years to complete, essentially turning a living tree into a solid quartz crystal.

Field identification & locations

Identify by looking for bark textures, wood grain patterns, and growth rings on a stone that is much heavier and harder than actual wood. Common in the Petrified Forest National Park and various sedimentary basins globally.