fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5–7 (Mohs scale); Color: Brown, black, dark grey; Luster: Dull/Waxy; Structure: Retains cellular structure of wood; Specific Gravity: 2.5–2.8.

Hardness: 6
Color: Brown, black, dark grey
Luster: Dull/Waxy

Identified July 9, 2026More fossil →

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Physical properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, black, dark grey; Luster: Dull/Waxy; Structure: Retains cellular structure of wood; Specific Gravity: 2.5–2.8.

Formation & geological history

Formed through permineralization where organic wood is replaced by silicate minerals (usually chalcedony or quartz) in an anaerobic environment, often following burial by volcanic ash or waterborne sediment. These specimens typically range from 20 to 300 million years old.

Uses & applications

Used for decorative ornaments, jewelry (cabochons), paperweights, and educational fossil collections.

Geological facts

Petrified wood is the state fossil of Washington and the state stone of Arizona. The famous Petrified Forest National Park contains trees from the Late Triassic epoch.

Field identification & locations

Identify in the field by looking for a rocky texture that preserves distinct wood grain, knots, or bark patterns. It feels much heavier than actual wood and cannot be scratched by a steel knife.