mineral

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Tan, brownish-grey, and black with visible wood grain; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz (Chalcedony/Agate); Specific gravity: 2.6-2.9

Hardness: 6
Color: Tan, brownish-grey, and black with visible wood grain
Luster: Vitreous to waxy

Identified June 29, 2026More mineral →

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: 6.5-7 (Mohs scale); Color: Tan, brownish-grey, and black with visible wood grain; Luster: Vitreous to waxy; Structure: Cryptocrystalline quartz (Chalcedony/Agate); Specific gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic wood materials are replaced by silica (Quartz) from groundwater over millions of years, often occurring in volcanic ash beds or river sediments during the Triassic to Cenozoic eras.

Uses & applications

Used for decorative ornaments, bookends, jewelry (cabochons), tiling, and as educational/collection specimens.

Geological facts

The specimen preserves the cellular structure of the original tree, making it a body fossil. Large concentrations are found in the Petrified Forest National Park in Arizona.

Field identification & locations

Identify in the field by looking for bark-like textures or growth rings on the exterior and a smooth, glass-like fracture on the interior. Often found in badlands or eroding sedimentary slopes.