fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5 to 7 on the Mohs scale. Color: Brown, tan, reddish-orange, grey, and black due to iron, manganese, and carbon impurities. Luster: Vitreous to earthy. Structure: Retains the fibrous cellular texture of original wood structure, microcrystalline quartz composition.

Hardness: 6
Luster: Vitreous to earthy

Identified July 23, 2026More fossil →

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Physical properties

Formation & geological history

Formed when plant material is buried by sediment and protected from decay due to oxygen deprivation. Mineral-rich water flowing through the sediment deposits minerals in the plant's cells. As the wood's lignin and cellulose decay, a stone mold is created in its place. Often dates from the Triassic through Tertiary periods.

Uses & applications

Used for decorative ornaments, lapidary art, bookends, jewelry (cabochons), polished display specimens, and as a popular collectible.

Geological facts

Petrified wood is the state fossil of Washington and Mississippi, and the state gem of Alberta. Arizona's Petrified Forest National Park contains one of the world's largest concentrations of petrified wood.

Field identification & locations

Identified by tree ring patterns, bark textures, and wood grain combined with the density and hardness of chalcedony/quartz. Found globally in ancient floodplains and volcanic ash deposits, notably in western North America, Madagascar, and Indonesia.