fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Gray, brown, tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.9

Hardness: 6
Color: Gray, brown, tan
Luster: Waxy to dull

Identified July 6, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Gray, brown, tan; Luster: Waxy to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None/Conchoidal fracture; Specific Gravity: 2.6-2.9

Formation & geological history

Formed when organic plant material is buried by sediment and undergoes permineralization, where groundwater rich in dissolved minerals (typically silica) replaces the organic matter while preserving anatomical details. Most specimens range from late Paleozoic to Cenozoic eras.

Uses & applications

Used for decorative landscaping, jewelry (cabochons), bookends, furniture tops, and as educational fossil specimens for collectors.

Geological facts

Unlike many fossils which are just impressions, petrified wood is a three-dimensional representation of the original organic material, often preserving growth rings and bark textures. The famous Petrified Forest National Park in Arizona is one of the world's most significant sites.

Field identification & locations

Identified in the field by its wood-like grain and bark texture combined with stony hardness and weight. It will not burn and is much denser than regular wood. Commonly found in sedimentary basins and volcanic ash beds.