fossil

Petrified Wood

Petrified Wood (Silicified Wood)

Hardness: 6.5-7 (Mohs), Color: Brown, gray, black, red, yellow, Luster: Waxy to dull, Crystal structure: Microcrystalline quartz (chalcedony) replacing organic structure, Cleavage: None, Specific gravity: 2.58-2.91

Hardness: 6

Identified July 18, 2026More fossil →

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Physical properties

Formation & geological history

Formed when plant material is buried by sediment and protected from decay due to lack of oxygen and organisms. Groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, pyrite, or another inorganic material such as opal. This process can take millions of years. Geological age varies widely, often from the Triassic, Jurassic, or Cretaceous periods.

Uses & applications

Used for display, lapidary work, jewelry, and sometimes in landscaping or decorative construction.

Geological facts

Petrified wood is the state gem of Washington state. The Petrified Forest National Park in Arizona is famous for its large concentrations of fossilized trees.

Field identification & locations

Identify by wood-like grain patterns, growth rings, and bark textures preserved in stone. Found worldwide, often in areas with past volcanic activity or sedimentary deposits. Collectors should look for clear wood structures and good color.