sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5–7 on Mohs scale; Color: Multi-colored earthy tones including brown, tan, red, and yellow; Luster: Vitreous to waxy; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.6–2.9

Hardness: 6
Luster: Vitreous to waxy

Identified June 16, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (usually silica/quartz) from groundwater while keeping the original structure. Commonly found in Mesozoic Era strata, particularly the Triassic period (~200 million years ago).

Uses & applications

Used in decorative arts, furniture (tabletops), jewelry (cabochons), and as museum-quality geological specimens.

Geological facts

Petrified wood is the state fossil of Arizona. The process happens in an anaerobic environment (without oxygen), which prevents aerobic decomposition, allowing minerals to seep into the cells.

Field identification & locations

Look for visible tree ring patterns, bark-like textures on the exterior, and a stony feel. Common locations include the Petrified Forest National Park (Arizona), Washington state, and Madagascar.