Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale. Color: Brown, tan, reddish-brown, often with dark layers. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (usually quartz replaceing cellulose). Specific gravity: 2.6–2.9.

Formation & Geological History

Formed through permineralization where organic wood materials are replaced by minerals (usually silica) while retaining the original structure of the tree. This specimen likely dates from the Triassic to the Tertiary periods.

Uses & Applications

Used for ornamental carvings, jewelry (cabochons), furniture tops, and as scientific fossils for paleobotanical study.

Geological Facts

Arizona's Petrified Forest National Park contains one of the world's largest concentrations of petrified wood. The mineral colors are caused by impurities: iron creates reds and yellows, manganese creates purples and blacks.

Field Identification & Locations

Identify by looking for preserved wood patterns, bark textures, or growth rings. Commonly found in areas with ancient volcanic ash or fluvial sedimentary deposits. Look for high density and hardness compared to standard wood.

Identified on: 5/20/2026

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