Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Brown, tan, reddish-brown; Luster: Dull to waxy; Crystal structure: Amorphous or microcrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6–2.9

Formation & Geological History

Formed through permineralization where organic wood material is replaced by minerals, typically silica, over millions of years in an anaerobic environment like volcanic ash or river sediments.

Uses & Applications

Used for ornamental carvings, jewelry (cabochons), furniture (slices for tabletops), and as decorative museum or collector specimens.

Geological Facts

Petrified wood is the state fossil of Arizona. The process preserves the cellular structure of the original tree so well that tree rings and bark patterns are often visible.

Field Identification & Locations

Identify by looking for wood-like grain, bark textures, and growth rings on a stone that is much heavier and harder than actual wood. Common in the Petrified Forest National Park (Arizona) and similar desert or volcanic regions.

Identified on: 5/20/2026

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