fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, colors range from brown and tan to green, red, and yellow, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz/chalcedony), no true cleavage, specific gravity around 2.5 to 2.7.

Identified August 7, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization, where organic wood material is buried in an oxygen-free environment by sediment or volcanic ash, and groundwater rich in dissolved silica replaces the organic matter cell-by-cell over millions of years.

Uses & applications

Used for ornamental objects, decorative bookends, lapidary art, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood can preserve the original cellular structure of ancient trees dating back hundreds of millions of years, sometimes even retaining tree rings.

Field identification & locations

Can be identified in the field by its distinct wood-like grain and texture combined with an unusually heavy weight and stone-like hardness. Common in regions with ancient forests buried by volcanic activity, such as Arizona's Petrified Forest.