sedimentary

Petrified Wood

Silicified wood (Quartz variant, SiO2)

Hardness: 6.5–7 on Mohs scale. Color: Gray, brown, or tan with wood-like textures. Luster: Vitreous to dull. Crystal structure: Cryptocrystalline (Microcrystalline quartz). Cleavage: None. Specific Gravity: 2.6–2.9.

Hardness: 6
Color: Gray, brown, or tan with wood-like textures
Luster: Vitreous to dull

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic materials are replaced with minerals (usually silica) while retaining the original structure of the wood. This process often takes millions of years, commonly occurring in Mesozoic or Cenozoic volcanic ash or sedimentary deposits.

Uses & applications

Used primarily for lapidary work, jewelry, interior decor (tabletops, bookends), and as an educational geological specimen.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona, USA. Some specimens are so well-preserved that tree rings and cellular structures can be seen under a microscope.

Field identification & locations

Identify in the field by looking for bark textures, concentric rings, or wood-like fibers on an extremely hard, heavy stone. It will not scratch with a pocketknife (unlike many sedimentary stones) and often feels colder to the touch than wood.

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