fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, colors range from brown, tan, and yellow to red and black depending on mineral impurities, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz/chalcedony), conchoidal fracture, specific gravity of 2.5 to 2.7.

Identified July 28, 2026More fossil →

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Physical properties

Formation & geological history

Formed when ancient trees were rapidly buried by sediment in an oxygen-poor environment, preventing decay. Over millions of years, groundwater rich in dissolved silica percolated through the wood, replacing the organic plant material cell-by-cell with minerals like quartz, opal, or chalcedony.

Uses & applications

Used primarily in lapidary arts, making decorative objects, bookends, jewelry, and as highly prized collector specimens.

Geological facts

Petrified wood retains the original cellular structure of the tree, allowing scientists to identify ancient plant species millions of years after they lived. The Petrified Forest National Park in Arizona is one of the most famous locations for these fossils.

Field identification & locations

Can be identified by its wood-like grain and bark texture combined with the heavy weight, cold feel, and hardness of stone. Found worldwide in sedimentary rock layers associated with ancient floodplains and volcanic ash beds.