mineral

Petrified Wood

Silicified Wood (SiO2 - Silicon Dioxide)

Hardness: 6.5–7 on Mohs scale; Color: Gray, brown, tan, with black and reddish oxidized iron streaks; Luster: Dull to waxy; Structure: Cryptocrystalline preserving cellular plant structure; Cleavage: None (conchoidal fracture).

Hardness: 6
Luster: Dull to waxy

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through permineralization, where organic wood material is replaced by silica (usually chalcedony or quartz) in an anaerobic environment, often buried by volcanic ash or river sediments. Most specimens range from the Devonian to the Pleistocene epochs (approx. 20 million to 390 million years old).

Uses & applications

Used in jewelry (cabochons), interior design (tabletops, bookends), fossil collecting, and lapidary arts. High-quality specimens are prized for educational museum displays.

Geological facts

Petrified wood is the state fossil of several US states, including Arizona and Washington. Despite being a 'rock,' it perfectly preserves the original tree rings and bark texture of the prehistoric plant it replaced.

Field identification & locations

Identify in the field by looking for bark-like exterior textures and internal concentric growth rings. Common in the Western United States (Petrified Forest National Park), Madagascar, and Indonesia. Collectors look for lack of decay and vibrant color patterns.

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