Petrified Wood

Physical Properties

Hardness: 6.5-7.0 on Mohs scale; Color: Gray, black, and brown due to carbon or iron oxides; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & Geological History

Formed when plant material is buried by sediment and protected from decay by oxygen. Groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with silica, calcite, or other minerals. Most common in Triassic to Tertiary deposits.

Uses & Applications

Used for decorative purposes, jewelry (cabochons), furniture (table tops), and as pedagogical and collector specimens.

Geological Facts

Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of permineralization. The Arizona Petrified Forest is one of the most famous global sites for these specimens.

Field Identification & Locations

Identify in the field by looking for characteristic bark texture or wood grain patterns that persist despite the material being hard stone. Often found in badlands or areas with eroded sedimentary strata.

Identified on: 5/20/2026

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