fossil

Petrified Wood

Silicified Wood (primarily quartz/chalcedony replacing organic wood structures, SiO2)

Hardness: 7 on the Mohs scale, Color: Brown, tan, reddish-brown, yellow, and white, Luster: Vitreous to waxy, Crystal Structure: Microcrystalline (cryptocrystalline quartz), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 - 2.7

Identified August 1, 2026More fossil →

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Physical properties

Formation & geological history

Forms through permineralization, where fallen trees are rapidly buried in sediment low in oxygen, preventing decay. Groundwater rich in dissolved silica flows through the wood, replacing organic matter cell-by-cell with quartz, chalcedony, or opal. Geological age ranges from millions to hundreds of millions of years old (Triassic to Cenozoic).

Uses & applications

Used for ornamental objects, high-end furniture, carvings, lapidary arts, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood can preserve the fine cellular structure of ancient trees down to the microscopic level. The world-famous Petrified Forest National Park in Arizona contains immense deposits dating back to the Late Triassic period, roughly 225 million years ago.

Field identification & locations

Identified in the field by retaining the outward shape, bark texture, or annual rings of wood, combined with an unusually heavy weight and high hardness that scratches glass. Common locations include the western United States, Argentina, and Madagascar.

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