sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish-brown
Luster: Vitreous to waxy

Identified June 28, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-brown; Luster: Vitreous to waxy; Crystal structure: Trigonal/Microcrystalline; Cleavage: None; Specific Gravity: 2.6-2.9

Formation & geological history

Formed via permineralization where organic wood materials are replaced by minerals (usually silica) while retaining original structure; typically dates from the Devonian to Holocene periods in low-oxygen burial environments.

Uses & applications

Used extensively in jewelry (cabochons), interior design (furniture, bookends), and as highly collectible ornamental specimens.

Geological facts

It is the state fossil of Arizona. Some specimens are so perfectly preserved that tree rings and cellular structures can still be observed under a microscope.

Field identification & locations

Identified by wood-like grain patterns, knots, or bark texture in a stony/glassy material; commonly found in the Petrified Forest National Park (AZ) and various riverbeds or sedimentary basins.