fossil

Petrified Wood

Silicified wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, orange, and grey due to iron/manganese oxides; Luster: Dull to waxy; Structure: Preserved botanical cellular structure replaced by cryptocrystalline quartz; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, tan, orange, and grey due to iron/manganese oxides
Luster: Dull to waxy

Identified July 14, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure. This occurs when woody debris is buried by sediment or volcanic ash in an anaerobic environment, typically during the Mesozoic or Cenozoic eras.

Uses & applications

Used for ornamental carvings, bookends, lapidary jewelry, furniture (tabletops), and highly valued by fossil collectors for scientific and aesthetic study.

Geological facts

Petrified wood is the state gem of Washington and the state fossil of Arizona. The largest concentration is found in the Petrified Forest National Park, featuring logs from the Triassic period roughly 225 million years ago.

Field identification & locations

Identify by looking for bark-like textures on the exterior and growth rings in cross-sections. In the field, look for heavy, stone-hard logs that resemble wood but don't rot. Found globally in ancient riverbeds or volcanic ash deposits.