fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on the Mohs scale, Color: Brown, tan, reddish-brown, and white with distinct grain patterns, Luster: Vitreous to waxy, Crystal Structure: Microcrystalline quartz (chalcedony/jasper), Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.7

Hardness: 6

Identified July 28, 2026More fossil →

Explore Petrified Wood in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through permineralization, where organic wood material is completely replaced by minerals (usually silica/quartz) over millions of years, typically occurring in sedimentary environments with volcanic ash. Often dates back to the Triassic period or younger (e.g., millions to hundreds of millions of years old).

Uses & applications

Used in ornamental stone carving, lapidary arts, jewelry, decorative tabletops, and highly sought after by fossil and mineral collectors.

Geological facts

Petrified wood retains the original cellular structure of the tree, allowing scientists to identify ancient plant species down to the microscopic level. Famous localities include the Petrified Forest National Park in Arizona.

Field identification & locations

Can be identified in the field by its distinct wood grain patterns and texture combined with an unusual weight and stone-like hardness. Common in regions with ancient riverbeds, volcanic ash layers, and sedimentary basins.