sedimentary

Petrified Wood

Silicified Wood (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Brown, tan, reddish, grey, Luster: Vitreous to waxy (when wet or polished), Crystal Structure: Microcrystalline quartz (chalcedony/jasper), Cleavage: None, Specific Gravity: 2.6-2.9

Hardness: 6

Identified June 25, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed via permineralization where organic wood is replaced by silica (usually chalcedony or opal) in an anaerobic environment, typically buried under volcanic ash or sedimentary flood deposits. Age ranges from the Paleozoic to the Cenozoic eras.

Uses & applications

Used for lapidary work, jewelry (cabochons), interior decor (tables, bookends), and as educational or collector specimens.

Geological facts

Unlike most fossils which are impressions, petrified wood is a three-dimensional replacement of original plant tissue, sometimes preserving cellular detail and bark textures. Some of the most famous sites like Petrified Forest National Park date back to the Triassic period.

Field identification & locations

Identified by wood-like growth ring patterns, bark-like exterior textures, and high hardness (cannot be scratched by a steel nail). It is commonly found in riverbeds, badlands, and areas with history of volcanic activity.