sedimentary

Petrified Wood

Silicified wood (primarily SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, reddish, and grey; Luster: Vitreous to dull; Crystal structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish, and grey
Luster: Vitreous to dull

Identified June 9, 2026More sedimentary →

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 is replaced by silica-rich minerals (quartz or opal) in anaerobic conditions. This specimen likely dates from the Triassic to the Cenozoic era.

Uses & applications

Used for interior decoration, jewelry (cabochons), furniture (slices for tables), and as educational fossils in collections.

Geological facts

The colors in petrified wood are caused by trace elements; for example, iron produces reds and yellows, while manganese creates pinks and oranges. Arizona's Petrified Forest National Park contains one of the world's largest concentrations.

Field identification & locations

Identify by looking for preserved wood grain, bark textures, or knots in a heavy, stony material. Commonly found in sedimentary basins and volcanic ash beds worldwide.