fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Shades of brown, grey, tan, and cream; Luster: Vitreous to waxy when polished; Crystal structure: Microcrystalline (Quartz/Chalcedony replacement); Cleavage: None; Specific gravity: 2.58-2.91.

Hardness: 6
Color: Shades of brown, grey, tan, and cream
Luster: Vitreous to waxy when polished

Identified July 24, 2026More fossil →

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Physical properties

Formation & geological history

Forms when plant material is buried by sediment and lack of oxygen prevents decay. Mineral-rich water flowing through the sediment deposits minerals in the plant cells, replacing original organic material with chalcedony or quartz over millions of years.

Uses & applications

Used in lapidary work, jewelry making, decorative home decor items, and popular among rock and mineral collectors.

Geological facts

Petrified wood can preserve the original tree rings and cellular structure of ancient plants down to a microscopic level. Arizona's Petrified Forest National Park contains one of the largest concentrations of petrified wood in the world.

Field identification & locations

Identified by wood grain or growth ring textures preserved inside a hard, heavy, quartz-like stone. Commonly found in ancient sedimentary basins, gravel bars, and volcanic ash deposits.