Petrified Wood (Silicified Wood)

Physical Properties

Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, white, and orange-red (due to iron oxides); Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None; Specific gravity: 2.6–2.9.

Formation & Geological History

Formed when plant material is buried by sediment (often volcanic ash) and permineralized. Over millions of years, silica-rich groundwater replaces the organic cell structure with minerals. This specimen likely dates from the Mesozoic or Cenozoic eras.

Uses & Applications

Used for lapidary work (jewelry, bookends, tabletops), decorative landscaping, and as educational/collector museum pieces.

Geological Facts

Petrified wood is the state fossil of Arizona, North Dakota, and Louisiana. Despite being made of stone, the internal structure can sometimes preserve tree rings and cell details visible under a microscope.

Field Identification & Locations

Identify by looking for wood-like textures (bark patterns, grain, knots) combined with the extreme hardness and weight of stone. Often found in badlands or areas with ancient sedimentary deposits.

Identified on: 4/17/2026

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