sedimentary

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Variegated brown, red, yellow, and grey; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific gravity: 2.6–2.9.

Hardness: 6
Color: Variegated brown, red, yellow, and grey
Luster: Vitreous to waxy

Identified April 9, 2026More sedimentary →

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Physical properties

Hardness: 6.5–7 (Mohs scale); Color: Variegated brown, red, yellow, and grey; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific gravity: 2.6–2.9.

Formation & geological history

Formed through permineralization, where organic wood material is replaced by minerals (usually silica) while retaining original structure. Most specimens date from the Devonian to the Pleistocene epochs, occurring in swampy, riverine, or volcanic ash environments.

Uses & applications

Used in ornamental jewelry (cabochons), lapidary arts, high-end furniture (tabletops), interior design accents, and as scientific/educational specimens.

Geological facts

Petrified wood is the state gemstone of Washington and the state fossil of Arizona. In some cases, the replacement is so perfect that microscopic cell structures and tree rings are preserved.

Field identification & locations

Identify by tree-ring-like structures and wood grain texture preserved in stone. Found globally, notably in the Petrified Forest National Park in Arizona, USA. Collectors look for vibrant colors and minimal fracturing.