sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness of 6.5 to 7 on the Mohs scale, featuring a waxy to vitreous luster and varicolored patterns of brown, yellow, red, and blue caused by mineral impurities during fossilization. It has a cryptocrystalline structure with no true cleavage.

Identified August 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed millions of years ago (often Triassic or Jurassic periods) when ancient trees were rapidly buried by sediment in an oxygen-poor environment, preventing decay. Groundwater rich in dissolved silica percolated through the wood, gradually replacing the organic cellular structure with quartz, chalcedony, or opal.

Uses & applications

Popular for lapidary work, decorative ornamental objects, cabochons for jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood can preserve the cellular structure of ancient trees in microscopic detail. The Petrified Forest National Park in Arizona contains one of the world's largest and most colorful concentrations of petrified wood.

Field identification & locations

Can be identified in the field by its distinct wood-like exterior shape and bark texture, combined with a heavy, stone-like weight and a conchoidal fracture revealing quartz-like material inside. Found worldwide, particularly in areas with ancient volcanic activity and sedimentary basins.