fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness of 7 on the Mohs scale, colors range from brown, red, and yellow to black depending on mineral impurities, vitreous to waxy luster, amorphous crystal structure (microcrystalline quartz/chalcedony), no true cleavage, specific gravity around 2.5 to 2.7.

Identified August 5, 2026More fossil →

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Physical properties

Formation & geological history

Forms when plant material is buried in an oxygen-depleted environment under sediment and slowly replaced by minerals—usually silica (quartz, chalcedony, or opal)—over millions of years. Geological age ranges from millions to hundreds of millions of years old.

Uses & applications

Used in lapidary arts, making decorative objects, jewelry, tabletops, and as highly prized specimens for fossil and mineral collections.

Geological facts

Famous locations include the Petrified Forest National Park in Arizona, USA. The original cellular structure of the wood is often preserved in microscopic detail during the fossilization process.

Field identification & locations

Can be identified in the field by its wood-like exterior texture and grain combined with an unusually heavy weight, cold touch, and a hard, glassy fracture characteristic of quartz. Found worldwide in sedimentary rock layers associated with ancient floodplains and volcanic ash deposits.