sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, cream, and white with wood grain textures; Luster: Vitreous to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, cream, and white with wood grain textures
Luster: Vitreous to waxy

Identified June 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) over millions of years. This specimen likely dates from the Triassic to Eocene periods, formed in low-oxygen environments like river deltas or volcanic ash beds.

Uses & applications

Used extensively for decorative lapidary work, jewelry (cabochons), furniture (slices for tabletops), and as prized museum/collector specimens.

Geological facts

The process can preserve the microscopic structure of the original wood, including tree rings and cell walls. The 'Petrified Forest' in Arizona contains some of the world's most famous and colorful specimens.

Field identification & locations

Identify in the field by looking for bark-like textures or growth rings on the exterior of stones that feel unusually heavy and hard. Commonly found in areas with historic volcanic activity or ancient floods, such as the Western US, Madagascar, and Indonesia.