fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on the Mohs scale. Color: Brown, tan, red, and black banding. Luster: Vitreous to waxy when polished. Crystal Structure: Microcrystalline (Quartz/Chalcedony replacement). Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Color: Brown, tan, red, and black banding
Luster: Vitreous to waxy when polished

Identified July 25, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization when plant material is buried by sediment under anaerobic conditions. Dissolved minerals in groundwater replace the organic wood fibers over millions of years, commonly dating from the Paleozoic to Cenozoic eras.

Uses & applications

Used for lapidary art, polished gemstones, cabochons, decorative sculptures, jewelry, and as educational collector specimens.

Geological facts

Petrified wood can retain even the microscopic cellular structure of the original tree, allowing paleobotanists to identify species that lived hundreds of millions of years ago.

Field identification & locations

Identify by tree ring patterns, bark-like textures, and high density compared to modern wood. Commonly found in Arizona (Petrified Forest National Park), Madagascar, Brazil, and Indonesia.