Petrified Wood

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Tan, brown, ochre, and black; Luster: Waxy to vitreous; Crystal structure: Microcrystalline (Trigonal); Cleavage: None; Specific Gravity: 2.58-2.91.

Formation & Geological History

Formed through permineralization, a process where organic wood materials are replaced by minerals (usually silica) while retaining the original wood structure. Most common during the Mesozoic Era (250 to 65 million years ago).

Uses & Applications

Used primarily for decorative objects, lapidary art, jewelry, and as educational geological specimens.

Geological Facts

Petrified wood is the state gem of Washington and the state rock of Mississippi. The largest concentrations are found in protected areas like Petrified Forest National Park in Arizona.

Field Identification & Locations

Identify in the field by looking for remnant bark textures, tree ring patterns, or wood grain structures preserved in a heavy, stone-like material. Often found in riverbeds or sedimentary basins.

Identified on: 4/21/2026

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