sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish; Luster: Vitreous to dull; Crystal structure: Microcrystalline quartz; Cleavage: None; Specific gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish
Luster: Vitreous to dull

Identified June 19, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish; Luster: Vitreous to dull; Crystal structure: Microcrystalline quartz; Cleavage: None; Specific gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (primarily silica) over millions of years, often in volcanic ash beds or sedimentary deposits.

Uses & applications

Used for decorative items, jewelry (cabochons), furniture tops, and as a popular collector specimen.

Geological facts

Petrified wood is the state fossil of Washington, Mississippi, and Arizona. The wood structure is often so perfectly preserved that growth rings and even cellular details are visible.

Field identification & locations

Identify by looking for wood-like grain, bark textures, and growth rings in a heavy, stony material. Commonly found in areas with past volcanic activity or ancient fluvial basins like the Petrified Forest National Park.