Rock Identifier
Petrified Wood with Lichen (Silicified Wood (SiO2) colonized by crustose lichens) — fossil
fossil

Petrified Wood with Lichen

Silicified Wood (SiO2) colonized by crustose lichens

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale (for the quartz/silica replacement); varied colors including tan, brown, black, and gray, accented by colorful yellow, orange, and gray lichen growths; waxy to vitreous luster on fresh breaks, dull where weathered or covered in lichen;…

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Physical properties

Hardness of 7 on the Mohs scale (for the quartz/silica replacement); varied colors including tan, brown, black, and gray, accented by colorful yellow, orange, and gray lichen growths; waxy to vitreous luster on fresh breaks, dull where weathered or covered in lichen; amorphous crystal structure as microcrystalline quartz (chalcedony/jasper).

Formation & geological history

Formed via permineralization, where organic wood material is buried in sediment under anoxic conditions and slowly replaced over millions of years by silica-rich groundwater. The specimen later became exposed on the surface and colonized by various species of crustose lichen.

Uses & applications

Used primarily as decorative collector specimens, lapidary work for display pieces, and educational displays showcasing fossilization and biological succession.

Geological facts

Petrified wood can preserve microscopic cellular structures of ancient trees dating back hundreds of millions of years. The growth of lichens on exposed petrified wood demonstrates how slow-growing organisms colonize durable siliceous substrates in natural environments.

Field identification & locations

Easily identified by retaining the wood-like grain and texture combined with the extreme hardness of quartz. Found worldwide in sedimentary deposits associated with ancient volcanic ash falls or river floodplains, such as the Petrified Forest in Arizona.

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