sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Dark brown, black, and tan; Luster: Vitreous to dull; Crystal structure: Amorphous to cryptocrystalline (chalcedony/quartz); Cleavage: None, conchoidal fracture.

Hardness: 6
Color: Dark brown, black, and tan
Luster: Vitreous to dull

Identified April 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 on Mohs scale; Color: Dark brown, black, and tan; Luster: Vitreous to dull; Crystal structure: Amorphous to cryptocrystalline (chalcedony/quartz); Cleavage: None, conchoidal fracture.

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic conditions, often under volcanic ash or river sediments. Geological age can range from Devonian to Pleistocene.

Uses & applications

Used for decorative items, jewelry (cabochons), lapidary art, furniture cross-sections, and educational geological collecting.

Geological facts

Unlike a cast, petrified wood is a three-dimensional fossil where the original cellular structure of the tree is often preserved in stone. The colors are caused by trace elements like iron, manganese, and copper.

Field identification & locations

Identify in the field by looking for bark-like textures, growth rings, or wood grain patterns in a heavy, stony material. Found globally in ancient floodplains and volcanic regions like Arizona and Patagonia.