fossil

Petrified Wood

Silicified wood (permineralized wood)

Hardness: 6.5-7 on the Mohs scale. Color: Varies widely including brown, grey, black, red, yellow, and white depending on mineral impurities. Luster: Vitreous to dull. Crystal structure: Microcrystalline quartz (chalcedony/jasper/opal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.5-2.7.

Hardness: 6
Luster: Vitreous to dull

Identified July 28, 2026More fossil →

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Physical properties

Formation & geological history

Formed when fallen trees are quickly buried in fine, oxygen-depleted sediment (such as volcanic ash or river mud) and slowly, over millions of years, groundwater rich in dissolved silica replaces the original organic wood cell walls with stone.

Uses & applications

Used for decorative items, jewelry, bookends, lapidary art, tabletops, and highly prized by fossil and mineral collectors.

Geological facts

Petrified wood can retain microscopic details of the original tree's growth rings and cell structure, allowing scientists to identify ancient species that lived millions of years ago.

Field identification & locations

Can be identified in the field by retaining the exterior texture, grain, and bark patterns of wood while feeling heavy like stone and exhibiting conchoidal fracture. Found worldwide, with famous deposits in the Petrified Forest National Park in Arizona, USA.