Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Multi-colored with dark brown, red, and black waxy lusters; Luster: Vitreous to greasy; Crystal Structure: Microcrystalline (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.6–2.9.

Formation & Geological History

Formed via permineralization where organic plant material is replaced by silica (usually chalcedony or quartz) over millions of years under burial conditions without oxygen. Most common specimens are from the Triassic, Jurassic, or Cenozoic periods.

Uses & Applications

Used largely for lapidary work, jewelry (cabochons), ornamental furniture, home decor (bookends, tabletops), and as a popular geological collectible.

Geological Facts

Petrified wood is the state fossil of Arizona. In some cases, the replacement is so precise that microscopic structures like tree rings and individual cells are preserved.

Field Identification & Locations

Identify in the field by looking for wood-like texture, bark patterns, or growth rings in stones that are too heavy and hard to be real wood. Common in the Colorado Plateau, USA, and Madagascar.

Identified on: 5/2/2026

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