fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, black, tan, and orange swirls; Luster: Vitreous to waxy (when polished); Structure: Cryptocrystalline (microscopic quartz fibers replacing organic wood); Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Brown, black, tan, and orange swirls
Luster: Vitreous to waxy (when polished)

Identified July 3, 2026More fossil →

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Physical properties

Formation & geological history

Formed through permineralization where wood is buried under sediment or volcanic ash. Over millions of years, mineral-rich groundwater replaces organic plant cells with silica/quartz, preserving the original structure. Geological age ranges from Devonian to Pleistocene.

Uses & applications

Used primarily for jewelry (cabochons), interior decoration (slabs, bookends, furniture), and as a popular educational geological specimen.

Geological facts

Petrified wood can sometimes preserve such fine detail that tree rings and even cell structures are visible under a microscope. The Petrified Forest National Park in Arizona is one of the world's most famous sites for these fossils.

Field identification & locations

Identify by looking for wood-like grain patterns, knots, or textures that have been transformed into hard, non-porous stone. Commonly found in sedimentary basins and volcanic regions worldwide.