sedimentary

Petrified Wood

Silicified Wood (primarily Quartz / Chalcedony: SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: Reddish-brown, tan, and grey; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6–2.9.

Hardness: 6
Color: Reddish-brown, tan, and grey
Luster: Vitreous to dull

Identified June 9, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 on Mohs scale; Color: Reddish-brown, tan, and grey; Luster: Vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.6–2.9.

Formation & geological history

Formed when organic plant material is buried by sediment or volcanic ash, protecting it from oxygen. Groundwater rich in dissolved minerals (usually silica) flows through the sediment, replacing the organic plant cells with minerals over millions of years. Most common during the Mesozoic Era.

Uses & applications

Used for ornamental carvings, jewelry (cabochons), lapidary work, high-end furniture (slabs), and as a popular geological collectible.

Geological facts

Petrified wood can preserve the cellular structure of original trees so accurately that the species can often be identified. The Painted Desert in Arizona contains one of the world's most famous concentrations of petrified logs.

Field identification & locations

Identify by looking for bark-like textures or growth rings on the exterior combined with a heavy, stone-like feel and extreme hardness (it will scratch glass). Commonly found in sedimentary basins and area of past volcanic activity.