Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Red, brown, tan; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None; Specific Gravity: 2.6–2.9

Formation & Geological History

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original structure of the wood. This typically occurs in sedimentary basins during the Triassic to Tertiary periods.

Uses & Applications

Used in lapidary arts for jewelry, bookends, furniture tops, and popular among geological collectors for its aesthetic and historical value.

Geological Facts

Petrified wood is the state giant fossil of Arizona. The Petrified Forest National Park in Arizona is one of the most famous locations for these specimens, dating back over 200 million years.

Field Identification & Locations

Identify by looking for preserved wood grain, bark textures, or growth rings in a stone that is much harder than wood. It is commonly found in riverbeds or volcanic ash deposits. Collectors should look for vibrant colors and visible cellular structures.

Identified on: 4/20/2026

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