sedimentary

Petrified Wood

Silicified Wood (SiO2)

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale; colors range from white, grey, and brown to vibrant reds and yellows due to mineral impurities; vitreous to waxy luster; cryptocrystalline or microcrystalline quartz structure; no true cleavage; specific gravity around 2.55-2.70.

Identified August 7, 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

Formation & geological history

Formed when ancient trees were rapidly buried by sediment, such as volcanic ash or river silt, in an anoxic environment that prevented decay. Over millions of years, groundwater rich in dissolved silica percolated through the organic material, replacing the original wood cellular structure with quartz, agate, or opal.

Uses & applications

Used primarily in lapidary arts for making cabochons, decorative carvings, bookends, jewelry, and as highly prized specimens for rock and mineral collectors.

Geological facts

Famous occurrences include the Petrified Forest National Park in Arizona, which features colorful logs dating back over 200 million years to the Triassic period. The replacement process is so precise that microscopic cell walls and ring structures can often be viewed under a microscope.

Field identification & locations

Identified by its preserved wood-like exterior textures, grain patterns, and ring structures combined with the heavy weight and conchoidal fracture of quartz. Common in regions with ancient sedimentary basins and volcanic activity.