fossil

Petrified Wood

Silicified wood (Quartz, SiO2)

Hardness of 6.5 to 7 on the Mohs scale; colors range from brown, tan, and red to yellow, white, and black depending on mineral impurities; vitreous to waxy luster; amorphous crystal structure; specific gravity ranges from 2.5 to 2.7.

Identified August 7, 2026More fossil →

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Physical properties

Formation & geological history

Formed when organic plant material is buried in an oxygen-depleted environment (such as volcanic ash or sedimentary mud) and groundwater rich in dissolved minerals (mainly silica) replaces the original cell structures cell-by-cell over millions of years.

Uses & applications

Used for ornamental objects, high-end lapidary work, jewelry, bookends, table tops, and prized by fossil and mineral collectors.

Geological facts

Petrified wood retains the exact cellular structure of the original tree, sometimes even preserving annual growth rings and bark texture.

Field identification & locations

Can be identified in the field by looking for wood-like grain, bark textures, or knot patterns combined with the heavy weight, cool feel, and conchoidal fracture of quartz. Found worldwide, with famous deposits in Arizona (Petrified Forest National Park) and Madagascar.