sedimentary

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

AI-generated identification · may be incorrect

Hardness: 6.5–7 Mohs; Color: Red, brown, orange, and gray due to iron and manganese impurities; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9

Hardness: 6
Luster: Waxy to vitreous

Identified February 21, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, where organic wood material is replaced by silica-rich groundwater while being buried under sediment, often volcanic ash, originating from the Triassic period (approx. 200 million years ago) or later.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), ornamental furniture (tabletops), and as highly collectible geological display specimens.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona; it is the state fossil of Arizona and is essentially a three-dimensional stone representation of an ancient tree.

Field identification & locations

Identify in the field by looking for stone specimens that retain the visual texture of wood grain, bark patterns, or growth rings. Common in badlands and areas with ancient river deposits.