sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, black, and cream banding. Luster: Vitreous to waxy when polished. Crystal structure: Cryptocrystalline (chalcedony/quartz). Cleavage: None. Specific gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, black, and cream banding
Luster: Vitreous to waxy when polished

Identified July 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic plant material is replaced by minerals, typically silica, in anaerobic conditions such as volcanic ash or river sediments. Dating from the Paleozoic to Cenozoic eras.

Uses & applications

Commonly used for decorative lapidary work, jewelry (cabochons), furniture (tabletops), and as educational museum or collector specimens.

Geological facts

Petrified wood is the state fossil of Arizona. The process of petrification occurs underground, protected from oxygen, and can preserve microscopic details of the original bark and woody tissue.

Field identification & locations

Identify by looking for wood-like growth rings, bark textures, or cellular structures preserved in stone. Commonly found in the Petrified Forest National Park (AZ), Madagascar, and Indonesia. Collectors look for high polish and vibrant color contrast.