sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale). Color: Brown, tan, and reddish hues. Luster: Vitreous to waxy. Crystal structure: Cryptocrystalline (chalcedony/quartz replacement). Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, tan, and reddish hues
Luster: Vitreous to waxy

Identified July 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic wood materials are replaced by minerals (primarily silica) over millions of years, often in volcanic ash beds or sedimentary river deposits during the Mesozoic or Cenozoic eras.

Uses & applications

Used in lapidary work for jewelry, bookends, furniture tops, and highly valued by fossil and mineral collectors.

Geological facts

Depending on the minerals present during formation, petrified wood can turn different colors: copper or chrome creates greens, while manganese creates pinks or oranges. Famous locations include the Petrified Forest National Park in Arizona.

Field identification & locations

Identified by preserved wood-like grain structures, growth rings, and bark textures occurring in a stone-hard material. Common in areas with historical volcanic activity or ancient floodplains.