sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, red, tan, and grey; Luster: Waxy to dull; Structure: Microcrystalline (preserving cellular plant structure); Cleavage: None; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, red, tan, and grey
Luster: Waxy to dull

Identified April 30, 2026More sedimentary →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness: 6.5-7 Mohs; Color: Brown, red, tan, and grey; Luster: Waxy to dull; Structure: Microcrystalline (preserving cellular plant structure); Cleavage: None; Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization when woody debris is buried by sediment and volcanic ash; over millions of years (often Triassic or Cenozoic), silica-rich groundwater replaces organic tissue with minerals.

Uses & applications

Used in gemstone jewelry, ornamental carvings, furniture (tabletops), and as highly collectible geological specimens.

Geological facts

The process preserves the wood so perfectly that tree rings and cellular structures are often visible under a microscope. Some of the most famous examples are found in Arizona's Petrified Forest National Park.

Field identification & locations

Identify by looking for wood-like grain and bark textures on a material that feels like stone and cannot be scratched by a steel blade. Commonly found in areas with ancient volcanic activity and sedimentary basins.