sedimentary

Petrified Wood

Silicified wood (principally SiO2)

AI-generated identification · may be incorrect

Hardness: 7 on Mohs scale; Color: Brown, grey, tan; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.9

Hardness: 7 on Mohs scale
Color: Brown, grey, tan
Luster: Vitreous to waxy

Identified June 28, 2026More sedimentary →

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

Hardness: 7 on Mohs scale; Color: Brown, grey, tan; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (microscopic quartz); Cleavage: None, conchoidal fracture; Specific gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (usually silica) while retaining the original wood structure. This process occurs underground under sediment, often over millions of years (commonly Mesozoic to Cenozoic eras).

Uses & applications

Used primarily for ornamental purposes, jewelry (cabochons), interior design (tabletops), and as highly collectible geological specimens.

Geological facts

Petrified wood is the state gemstone of Arizona. The cell structure of the original tree is often so well preserved that the species of the tree can be identified under a microscope.

Field identification & locations

Identify by looking for visible tree rings or bark-like textures on the exterior. It is much heavier and harder than normal wood. Common locations include Arizona (Petrified Forest National Park), Madagascar, and Indonesia.