mineral

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs); Color: Tan, brown, black, and white banding; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline quartz); Cleavage: None, conchoidal fracture

Hardness: 6
Color: Tan, brown, black, and white banding
Luster: Vitreous to waxy

Identified May 3, 2026More mineral →

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); Color: Tan, brown, black, and white banding; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline quartz); Cleavage: None, conchoidal fracture

Formation & geological history

Formed through permineralization where organic wood materials are replaced by minerals (primarily silica) over millions of years, often in volcanic ash or sedimentary basins during the Mesozoic or Cenozoic eras.

Uses & applications

Used for lapidary work, jewelry (cabochons), interior decor, landscaping, and as a popular teaching and collector specimen.

Geological facts

The entire process must occur in an anaerobic environment (without oxygen) to prevent rot before the minerals can stabilize the cell structure; entire forests have been preserved this way, such as the Petrified Forest National Park in Arizona.

Field identification & locations

Identify in the field by looking for bark textures, growth rings, or wood-like grain in a heavy, stone-hard material. Common in areas with historical volcanic activity and sedimentary rivers.