Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale. Color: Gray, brown, white, tan. Luster: Vitreous to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None, conchoidal fracture.

Formation & Geological History

Formed through permineralization where organic plant matter is replaced by minerals, typically silica from volcanic ash, over millions of years (commonly Carboniferous to Cenozoic eras) in anaerobic environments.

Uses & Applications

Used in jewelry (lapidary), decorative ornaments, furniture tops, and as educational/collector specimens.

Geological Facts

Petrified wood is the state fossil of Washington and several other US states. Most specimens contain the original cell structure of the tree perfectly preserved in stone.

Field Identification & Locations

Identify by looking for bark-like textures, growth rings, and woody grain patterns on a rock that feels much heavier and harder than actual wood. Found in areas with historic volcanic activity and river basins.

Identified on: 5/2/2026

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