sedimentary

Petrified Wood

Silicified wood (principally Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: typically shades of gray, brown, or tan with wood grain patterns; Luster: waxy to vitreous; Crystal structure: cryptocrystalline (as quartz or chalcedony); Cleavage: none, conchoidal fracture; Specific gravity: 2.6–2.9.

Hardness: 7 on Mohs scale
Luster: waxy to vitreous

Identified March 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, where organic wood material is replaced by minerals (usually silica) in a low-oxygen environment, such as burial under volcanic ash or sediment. Occurs over millions of years, often dating to the Triassic, Jurassic, or Cenozoic eras.

Uses & applications

Used in ornamental jewelry (cabochons), interior design (tabletops, bookends), landscaping, and as educational geological specimens.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona, USA. Though it appears to be wood, it contains no original biological material; the cell structure is perfectly preserved in stone.

Field identification & locations

Identify in the field by looking for bark textures, growth rings, and wood-like structures combined with the heavy weight and hardness of stone. Found in ancient riverbeds or volcanic ash deposits worldwide.

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