fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, cream, and white. Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline (chalcedony/quartz). Cleavage: None; conchoidal fracture. Specific Gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, cream, and white
Luster: Vitreous to waxy

Identified July 1, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization where organic wood materials are replaced by silica (quartz) from groundwater while buried under sediment or volcanic ash. This typically occurs over millions of years, often dating back to the Triassic or Cenozoic eras.

Uses & applications

Used extensively in jewelry, lapidary arts, such as bookends and tabletops, and as a popular collector's specimen. Known for its decorative beauty when polished.

Geological facts

The Arizona Petrified Forest is one of the most famous locations for these specimens. Despite being stone, the original grain, bark, and ring patterns of the tree are often perfectly preserved at a cellular level.

Field identification & locations

Identify by looking for distinct wood-like grain or rings on a hard, stony surface that cannot be scratched by a steel knife. Common in areas with ancient volcanic activity and sedimentary basins.