fossil

Petrified Wood

Silicified wood (primarily quartz replacing organic cellulose)

Hardness: 7 on the Mohs scale; Color: Tan, brown, white, and reddish-brown; Luster: Vitreous to dull; Crystal structure: Microcrystalline quartz (chalcedony/jasper); Cleavage: None (conchoidal fracture); Specific gravity: 2.5 - 2.7

Hardness: 7 on the Mohs scale
Color: Tan, brown, white, and reddish-brown
Luster: Vitreous to dull

Identified July 30, 2026More fossil →

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Physical properties

Formation & geological history

Formed when fallen trees are rapidly buried in sediment-rich, oxygen-depleted environments such as volcanic ash or floodplains, preventing decay. Over millions of years, groundwater rich in dissolved silica permeates the wood, replacing the organic matter cell-by-cell with quartz or other minerals while preserving the original structural details.

Uses & applications

Popular for lapidary work, making ornamental objects, bookends, jewelry, and prized by fossil and mineral collectors.

Geological facts

Petrified wood can retain its microscopic cellular structure so perfectly that scientists can identify the exact ancient tree species. The Petrified Forest National Park in Arizona contains some of the world's most famous and vibrant deposits dating back to the Late Triassic period, roughly 225 million years ago.

Field identification & locations

Can be identified in the field by its distinct wood-like grain, bark texture, and weight, as it is much heavier than normal wood due to its stone composition. Often found in sedimentary strata associated with ancient river systems and volcanic ash beds worldwide.

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