sedimentary

Petrified Wood

Siliconized Wood (SiO2)

Hardness: 6.5–7; Color: Red, brown, pink, tan (due to iron oxides); Luster: Waxy to vitreous; Structure: Microcrystalline (preserving organic cellular structure); Specific Gravity: 2.6–2.9.

Hardness: 6
Color: Red, brown, pink, tan (due to iron oxides)
Luster: Waxy to vitreous

Identified June 8, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7; Color: Red, brown, pink, tan (due to iron oxides); Luster: Waxy to vitreous; Structure: Microcrystalline (preserving organic cellular structure); Specific Gravity: 2.6–2.9.

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining original structures. Most specimens date from the Triassic to the Tertiary periods in riverbed or volcanic ash environments.

Uses & applications

Used for lapidary work, jewelry (cabochons), ornamental furniture, and geological collecting.

Geological facts

The largest concentration of petrified wood is in the Petrified Forest National Park in Arizona. It is the state fossil of Arizona, North Dakota, and Louisiana.

Field identification & locations

Identify by looking for wood-like grain, growth rings, or bark textures on the exterior. Found globally in ancient floodplains or areas with high volcanic ash deposition.