sedimentary

Petrified Wood (Agatized/Silicified Wood)

Silicified Wood (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Dark brown to black, Luster: Vitreous to dull, Crystal Structure: Cryptocrystalline (Microcrystalline Quartz), Cleavage: None, Specific Gravity: 2.6-2.9

Hardness: 6

Identified June 12, 2026More sedimentary →

Explore Petrified Wood (Agatized/Silicified 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: Dark brown to black, Luster: Vitreous to dull, Crystal Structure: Cryptocrystalline (Microcrystalline Quartz), Cleavage: None, Specific Gravity: 2.6-2.9

Formation & geological history

Formed via permineralization where organic plant matter is replaced by silica minerals (usually chalcedony or quartz) over millions of years in anaerobic sedimentary environments. This specimen likely dates back to the Triassic or Jurassic period.

Uses & applications

Used in jewelry (lapidary), ornamental furniture, home decor, and educational/scientific collecting.

Geological facts

Petrified wood is the official state fossil of Arizona. The organic cellular structure is often preserved so perfectly that tree rings and bark patterns can be studied under a microscope.

Field identification & locations

Identify by looking for distinct wood grain patterns or bark-like textures in a heavy, cold-to-the-touch stony material. Common in areas like the Petrified Forest National Park (Arizona), Madagascar, and Indonesia.