fossil

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, grey with visible banding; Luster: Vitreous to waxy; Texture: Fine-grained with preserved wood grain; Cleavage: None (conchoidal fracture)

Hardness: 6
Color: Brown, tan, grey with visible banding
Luster: Vitreous to waxy

Identified July 7, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, grey with visible banding; Luster: Vitreous to waxy; Texture: Fine-grained with preserved wood grain; Cleavage: None (conchoidal fracture)

Formation & geological history

Formed through permineralization over millions of years (often Mesozoic or Cenozoic). Organic wood cells are replaced by minerals, typically silica (quartz or chalcedony), in an anaerobic environment like volcanic ash or river silt.

Uses & applications

Used for decorative items, jewelry (cabochons), furniture (heavy slabs), and as educational or geological collectibles.

Geological facts

Petrified wood is the state fossil of several US states, including Arizona and Washington. It can perfectly preserve the tree's growth rings and cellular structure down to the microscopic level.

Field identification & locations

Identify by looking for distinct bark-like textures or growth rings in a heavy, stone-like material. Often found in specific 'Petrified Forest' regions or riverbeds where erosion exposes ancient layers.