fossil

Petrified Wood

Silicified Wood (SiO2)

Mohs hardness of 6.5 to 7; colors vary widely including red, brown, yellow, and grey due to mineral impurities; vitreous to waxy luster; amorphous crystal structure as the original organic material is replaced by microcrystalline quartz (chalcedony or jasper); conchoidal fracture with no true cleavage;…

Identified August 4, 2026More fossil →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in sediment low in oxygen, preventing decay. Over millions of years, groundwater rich in dissolved silica flows through the sediment, replacing the organic wood cells with quartz or other minerals while preserving the original cellular structure.

Uses & applications

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

Geological facts

Petrified wood can retain its original wood grain, ring patterns, and even bark texture down to the microscopic cell level despite being entirely stone.

Field identification & locations

Identified by retaining the external shape and texture of wood while exhibiting the high hardness, weight, and conchoidal fracture of quartz. Commonly found in regions with ancient volcanic activity and sedimentary basins, such as the Petrified Forest National Park in Arizona.