fossil

Petrified Wood

Silicified Paleoxylon (SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Brown, tan, cream, and reddish hues. Luster: Dull to waxy or vitreous when polished. Crystal structure: Cryptocrystalline (Microcrystalline quartz). Cleavage: None, conchoidal fracture. Specific gravity: 2.6–2.9.

Hardness: 6
Color: Brown, tan, cream, and reddish hues
Luster: Dull to waxy or vitreous when polished

Identified July 5, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure of the wood. This specimen likely dates from the Paleozoic to Cenozoic eras (millions of years old).

Uses & applications

Used for ornamental purposes, jewelry (cabochons), interior design (tables or bookends), and as educational fossils for collectors.

Geological facts

Petrified wood is the state gemstone of Washington and the state fossil of North Dakota. Entire forests, such as the Petrified Forest National Park in Arizona, have been preserved this way.

Field identification & locations

Identify in the field by looking for bark textures, growth rings, and wood grain patterns on heavy, hard stone. Common in sedimentary basins and volcanic ash beds. Avoid collecting in protected national parks.