fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, and cream with visible wood grain; Luster: Dull to waxy; Structure: Pseudomorph of quartz after cellulose; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, and cream with visible wood grain
Luster: Dull to waxy

Identified July 8, 2026More fossil →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, tan, and cream with visible wood grain; Luster: Dull to waxy; Structure: Pseudomorph of quartz after cellulose; Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization, where organic materials are replaced by minerals (usually silica) in subterranean environments over millions of years, often dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used for decorative garden stones, lapidary work (jewelry, bookends), and educational fossil collections.

Geological facts

Petrified wood is the state stone of Washington and the state fossil of Arizona. The process requires an anaerobic environment to prevent rot while minerals seep in via groundwater.

Field identification & locations

Identify by looking for distinct growth rings, bark textures, and cellular structures that look like wood but feel like stone. Common in the Petrified Forest National Park (Arizona) and similar sedimentary basins worldwide.