sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7.0 (Mohs scale), Color: Brown, red, grey, and black due to iron and manganese oxides, Luster: Vitreous to dull, Crystal Structure: Cryptocrystalline (usually replaced by quartz/chalcedony), Cleavage: None, Specific Gravity: 2.6-2.9

Hardness: 6

Identified June 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic remains of trees are replaced by minerals (usually silica) while retaining the original structure of the wood. This typically occurs in sedimentary environments during periods like the Triassic or Eocene.

Uses & applications

Used primarily for decorative objects, jewelry (cabochons), furniture (stone tabletops), and as prized specimens for geological collectors.

Geological facts

The fossil record of petrified wood dates back millions of years. Famous locations includes the Petrified Forest National Park in Arizona, USA. It is the official state fossil of Arizona and the state stone of Washington.

Field identification & locations

Identify in the field by checking for wood-grain patterns, knots, or bark textures on a stone that is much heavier and harder than actual wood. It often appears as chunks of logs or splinters that break with a conchoidal fracture.