sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, green, or red due to minerals; Luster: Vitreous to dull; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific gravity: 2.6–2.9.

Hardness: 6
Color: Brown, tan, green, or red due to minerals
Luster: Vitreous to dull

Identified June 9, 2026More sedimentary →

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: Brown, tan, green, or red due to minerals; Luster: Vitreous to dull; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific gravity: 2.6–2.9.

Formation & geological history

Formed through permineralization when woody plant material is buried under sediment or volcanic ash. Over millions of years (often 20-300 million years), silica-rich groundwater replaces the organic matter with agate, opal, or jasper.

Uses & applications

Used primarily for ornamental purposes, jewelry (lapidary), interior design (tabletops/bookends), and as a valuable collector's geological specimen.

Geological facts

Whole fossilized forests exist, such as the Petrified Forest National Park in Arizona. The various colors are caused by trace elements: iron creates reds/oranges, while copper or chromium can create greens.

Field identification & locations

Identify in the field by looking for 'bark' textures or visible tree rings in stone. Commonly found in areas with past volcanic activity or ancient floodplains like Arizona, Madagascar, and Indonesia.