fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale), Color: tan, brown, beige, and cream, Luster: dull to waxy, Crystal Structure: Cryptocrystalline quartz (chalcedony/opal), Cleavage: none (conchoidal fracture)

Hardness: 6

Identified July 20, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale), Color: tan, brown, beige, and cream, Luster: dull to waxy, Crystal Structure: Cryptocrystalline quartz (chalcedony/opal), Cleavage: none (conchoidal fracture)

Formation & geological history

Formed via permineralization when woody plant material is buried by sediment or volcanic ash, and water rich in dissolved silica flows through, replacing organic cells with minerals. Typically millions of years old.

Uses & applications

Used for home decor, lapidary arts, jewelry (cabochons), and as museum or collector specimens. Larger logs are used for furniture such as tabletops.

Geological facts

Unlike most fossils which are impressions, petrified wood is a 3D mineralized representation of the original organic matter. Famous sites include the Petrified Forest National Park in Arizona, USA.

Field identification & locations

Identify in the field by looking for stone that retains the texture of bark, wood grain, or growth rings. Found globally in ancient sedimentary basins. Collectors look for high color contrast and preservation of cellular structure.