fossil

Petrified Wood

Silicified wood (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, black, tan, grey; Luster: Waxy to vitreous (especially when wet or polished); Crystal structure: Microcrystalline quartz; Cleavage: None, exhibits conchoidal fracture.

Hardness: 6
Color: Brown, black, tan, grey
Luster: Waxy to vitreous (especially when wet or polished)

Identified July 15, 2026More fossil →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic wood materials are replaced by minerals (usually silica) over millions of years, typically occurring when wood is buried under sediment or volcanic ash. Common in Triassic to Tertiary deposits.

Uses & applications

Used primarily in lapidary work for making jewelry, ornaments, furniture (like tabletops), and as decorative display specimens for collectors.

Geological facts

Petrified wood is the state fossil of Arizona and Washington. It can preserve the microscopic details of the original tree bark and rings so perfectly that the species of tree can be identified.

Field identification & locations

Identified by the preservation of woody grain, knots, and bark textures in a heavy, stony material. Found in abundance in the American Southwest, Madagascar, and Indonesia. Look for 'log' shapes that do not rot.