sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Tan, brown, grey, and cream; Luster: Waxy to vitreous; Crystal structure: Microcrystalline (Cryptocrystalline) quartz; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Tan, brown, grey, and cream
Luster: Waxy to vitreous

Identified June 23, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Tan, brown, grey, and cream; Luster: Waxy to vitreous; Crystal structure: Microcrystalline (Cryptocrystalline) quartz; Cleavage: None (conchoidal fracture).

Formation & geological history

Process of permineralization where organic wood material is replaced by minerals, typically silica, after being buried in sediment/volcanic ash. Often millions of years old (frequently Paleozoic to Cenozoic).

Uses & applications

Used for home decor, lapidary arts like bookends and tabletops, jewelry (cabochons), and as museum or collector specimens.

Geological facts

Sometimes the replacement is so perfect that cell structures and tree rings are visible under a microscope. Arizona's Petrified Forest National Park contains one of the world's largest concentrations of it.

Field identification & locations

Identify in the field by looking for wood-like textures (bark, rings) combined with a stony, heavy, and hard surface that cannot be scratched by a steel pocketknife. Common in sedimentary basins.