Petrified Wood

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Red, brown, yellow, grey, and black; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None; Specific gravity: 2.6-2.9.

Formation & Geological History

Formed through permineralization, where organic wood material is replaced by minerals (usually silica) in anaerobic conditions, often under volcanic ash or sediment. Many specimens date to the Triassic, Jurassic, or Cenozoic eras.

Uses & Applications

Used for ornamental furniture, jewelry (cabochons), interior design, education, and as a popular lapidary or museum collector's item.

Geological Facts

Famous locations include the Petrified Forest National Park in Arizona. Because the silica replacement captures the biological structure at a cellular level, tree rings and bark patterns are often perfectly preserved in stone.

Field Identification & Locations

Identify in the field by looking for wood-grain textures, bark-like exteriors, or annual growth rings in a heavy, stony material. Common in areas with a history of volcanic activity and ancient fluvial systems.

Identified on: 4/25/2026

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