fossil

Petrified Wood

Silicified wood / Xylopal

Hardness: 7 on the Mohs scale. Color: Brown, reddish-brown, tan, and grey with visible growth rings and cellular structure. Luster: Vitreous to waxy when polished. Crystal structure: Microcrystalline quartz (chalcedony/jasper). Specific gravity: 2.5 - 2.7.

Hardness: 7 on the Mohs scale
Luster: Vitreous to waxy when polished

Identified July 29, 2026More fossil →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in fine, oxygen-depleted sediments such as volcanic ash or river silt, allowing groundwater rich in dissolved silica to slowly replace the organic wood tissues with stone over millions of years (often Triassic to Cenozoic eras).

Uses & applications

Used for ornamental carvings, decorative tabletops, jewelry, metaphysical purposes, and as prized specimens for fossil and mineral collectors.

Geological facts

Petrified wood can preserve microscopic details of ancient plant structures down to the cellular level. The Petrified Forest National Park in Arizona contains one of the world's largest concentrations of petrified logs.

Field identification & locations

Easily identified by its retained external tree bark or internal wood grain texture coupled with an unexpectedly heavy weight and high hardness that scratches glass. Found worldwide in sedimentary rock layers associated with ancient forests and volcanic ash beds.