sedimentary

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, grey, or multi-colored depending on mineral impurities; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None/Conchoidal fracture.

Hardness: 6
Luster: Waxy to vitreous

Identified June 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic plant material is replaced by minerals, typically silica, from groundwater while buried in sediment or volcanic ash. Typical ages range from Devonian to Pleistocene (approx. 390 to 2 million years old).

Uses & applications

Used for lapidary work, jewelry (cabochons), ornamental furniture (table slabs), landscaping, and as a popular educational geological specimen.

Geological facts

Petrified wood is the state fossil of Arizona. The organic matter is often replaced so perfectly that cell structures and tree rings remain visible under a microscope.

Field identification & locations

Identify by looking for bark-like textures and growth rings on an object that feels like stone. Found globally, with famous deposits in the Petrified Forest National Park, Arizona, and Madagascar.