Petrified Wood

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, gray, tan, or black with visible wood grain; Luster: Dull to waxy/vitreous; Structure: Microcrystalline quartz replacing organic cellulose; Specific Gravity: 2.6-2.9.

Formation & Geological History

Formed through permineralization when plant material is buried by sediment or volcanic ash and saturated with mineral-rich groundwater over millions of years (often from the Triassic, Jurassic, or Cretaceous periods).

Uses & Applications

Used primarily for lapidary work, jewelry (cabochons), ornamental furniture, museum displays, and as a popular collector's specimen.

Geological Facts

Petrified wood is the state stone of Arizona. It preserves the cellular structure of the original tree so well that scientists can often identify the specific prehistoric species of the plant.

Field Identification & Locations

Identify in the field by looking for distinct wood grain, bark textures, or growth rings in a heavy, stony material. Found globally, notably in the Petrified Forest National Park (Arizona) and Madagascar.

Identified on: 5/2/2026

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