sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5 to 7 on the Mohs scale. Color: Varies widely including brown, black, red, yellow, and white depending on mineral impurities like iron and manganese oxides. Luster: Vitreous to dull. Crystal structure: Microcrystalline quartz (chalcedony/jasper). Cleavage: None, exhibits conchoidal fracture.…

Hardness: 6
Luster: Vitreous to dull

Identified August 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization when organic plant material is rapidly buried in an oxygen-poor environment such as volcanic ash or sedimentary mud, allowing groundwater rich in dissolved silica to slowly replace the original cellular structure with quartz over millions of years.

Uses & applications

Used primarily in lapidary arts, decorative items, bookends, jewelry, and as a popular specimen for fossil and mineral collectors.

Geological facts

Petrified wood can preserve microscopic cellular details of ancient trees that lived millions of years ago, sometimes dating back to the Triassic period or earlier. The Petrified Forest in Arizona is one of the most famous localities in the world.

Field identification & locations

Can be identified in the field by its distinct wood-like exterior texture combined with a stone-like weight, conchoidal fracture, and ability to scratch glass due to its quartz composition. Found worldwide in ancient floodplains and volcanic ash deposits.