sedimentary

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Hardness: 6.5–7 on Mohs scale. Color: Tan, brown, reddish-pink. Luster: Vitreous to dull. Structure: Microcrystalline (preserving organic cellular structure). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.7.

Hardness: 6
Color: Tan, brown, reddish-pink
Luster: Vitreous to dull

Identified March 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization over millions of years (often Mesozoic or Cenozoic). Organic matter is replaced by silica/chalcedony from groundwater while buried under sediment or volcanic ash, preserving the wood's anatomical structure.

Uses & applications

Used for ornamental carvings, jewelry (cabochons), furniture (tabletops), and display pieces for geological collectors.

Geological facts

The process is so precise that microscopic structures like tree rings and individual cells are often preserved. Arizona's Petrified Forest National Park contains some of the world's most famous Triassic-age specimens.

Field identification & locations

Identify by looking for distinct bark-like textures or growth rings on a stone that is too hard to be scratched by a steel knife. Common in areas with ancient volcanic activity and old sedimentary basins like the Western United States, Madagascar, and Indonesia.

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