fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs); Color: Tan, cream, and beige; Luster: Dull to waxy; Texture: Preserved woody grain or bark-like appearance; Crystal Structure: Microcrystalline quartz (Chalcedony/Agate)

Hardness: 6
Color: Tan, cream, and beige
Luster: Dull to waxy

Identified July 3, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs); Color: Tan, cream, and beige; Luster: Dull to waxy; Texture: Preserved woody grain or bark-like appearance; Crystal Structure: Microcrystalline quartz (Chalcedony/Agate)

Formation & geological history

Formed via permineralization where organic wood is replaced by silica-rich minerals (quartz) in an anaerobic environment, usually under volcanic ash or sedimentary layers. Process occurs over millions of years, often dating to the Triassic through Cenozoic eras.

Uses & applications

Used for decorative ornaments, jewelry (cabochons), furniture (slices for tables), museum displays, and as a popular educational geological specimen.

Geological facts

Petrified wood is the state fossil of Arizona. The Petrified Forest National Park contains some of the world's most famous and colorful deposits, dating back about 225 million years.

Field identification & locations

Identify by looking for cellular structures, growth rings, or bark textures on a stone that feels heavy and cold like quartz. Common in arid regions with sedimentary basins like Arizona, Madagascar, and Indonesia.