fossil

Petrified Wood

Silicified wood (Quartz/Chalcedony replacement of cellulose)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (Microscopic quartz); Cleavage: None/Conchoidal fracture.

Hardness: 6
Color: Brown, tan, reddish
Luster: Waxy to dull

Identified July 20, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish; Luster: Waxy to dull; Crystal structure: Cryptocrystalline (Microscopic quartz); Cleavage: None/Conchoidal fracture.

Formation & geological history

Formed through permineralization, a process where organic wood materials are replaced by minerals (usually silica) while retaining the original wood structure. Most common in sedimentary environments like river deltas after burial by volcanic ash or silt.

Uses & applications

Used for ornamental purposes, jewelry (cabochons), large decorative slabs, bookends, and as a popular scientific/geological collectible.

Geological facts

Petrified wood is the state fossil of Arizona. The cell structure is often so perfectly preserved that a microscope can determine the original species of the extinct tree.

Field identification & locations

Identify by looking for characteristic wood grain, rings, or bark textures in a heavy, stone-like material. Common in regions with high volcanic history like Arizona (Petrified Forest National Park) and Washington state.

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