sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Tans, grays, and browns (due to iron and manganese oxides); Luster: Vitreous to dull; Structure: Cryptocrystalline quartz (chalcedony/opal); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.7.

Hardness: 6
Color: Tans, grays, and browns (due to iron and manganese oxides)
Luster: Vitreous to dull

Identified April 10, 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, a process where organic material is replaced by minerals (usually silica) while retaining the original woody structure. This typically occurs when wood is buried under volcanic ash or sediment in an anaerobic environment. Samples can range from 20 to 300 million years old.

Uses & applications

Used primarily for jewelry (cabochons), lapidary art, home decor (bookends, tables), and by geological collectors. It also serves as a valuable record for paleobotany.

Geological facts

Arizona's Petrified Forest National Park contains one of the world's most famous deposits. While it looks like wood, it is entirely stone; the mineral replacement is so precise that cell structures and growth rings can often be seen under a microscope.

Field identification & locations

Identify in the field by looking for 'bark' textures on the exterior and growth ring patterns on cross-sections. It is found globally in regions with ancient sedimentary basins, such as the American West, Argentina, and Egypt.