sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Variegated reds, browns, whites, and greys; Luster: Waxy to vitreous; Structure: Cryptocrystalline (Quartz/Chalcedony); Cleavage: Conchoidal fracture; SG: 2.6-2.9.

Hardness: 6
Color: Variegated reds, browns, whites, and greys
Luster: Waxy to vitreous

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) in anaerobic conditions, often under volcanic ash or sediment layers. Most common during the Triassic through Eocene periods.

Uses & applications

Used in furniture making (tabletops), jewelry (cabs), lapidary art, and popular as cabinet specimens for collectors.

Geological facts

In 'agatized' specimens, the replacement is so perfect that the microscopic cell structure of the original tree remains visible. The Petrified Forest National Park in Arizona is the most famous locality for these specimens.

Field identification & locations

Identify in the field by looking for bark textures on the exterior and a smooth, waxy fracture surface on the interior that resembles chert or agate. Found globally in ancient riverbeds or volcanic regions.