sedimentary

Petrified Wood (Agatized/Silicified Wood)

Silicified Paleoxylon (primarily SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Black, dark brown, or charcoal; Luster: Resinous to vitreous; Crystal Structure: Cryptocrystalline (chalcedony/quartz replaces organic matter); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Black, dark brown, or charcoal
Luster: Resinous to vitreous

Identified June 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization over millions of years (typically Triassic to Tertiary periods). Organic material is replaced by minerals, usually silica, from groundwater while buried under sediment or volcanic ash in an anaerobic environment.

Uses & applications

Used for ornamental carvings, jewelry (lapidary), architectural slabs, and highly valued as geological collector specimens.

Geological facts

Petrified wood retains the original cellular structure of the wood, allowing paleobotanists to identify the specific tree species that lived millions of years ago. Arizona's Petrified Forest National Park contains some of the world's most famous deposits.

Field identification & locations

Identify by the presence of wood grain, bark textures, or growth rings preserved in stone. This specific dark, carbonaceous specimen can be found in coal-bearing formations or volcanic ash layers. It will be much heavier than normal wood and cool to the touch.

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