Petrified Wood

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, tan, and grey with wood-grain patterns; Luster: Vitreous to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.6-2.9

Formation & Geological History

Formed when plant material is buried by sediment and protected from decay by organisms and oxygen. Groundwater rich in dissolved solids flows through the sediment, replacing original plant material with silica, calcite, or pyrite over millions of years.

Uses & Applications

Used for making jewelry, bookends, tabletops, and as a popular collector's item in lapidary arts.

Geological Facts

Petrified wood is the state fossil of Washington and Arizona. Some of the most famous deposits are found in the Petrified Forest National Park in Arizona, dating back to the Triassic period.

Field Identification & Locations

Identify by looking for characteristic wood-like textures, grain patterns, and bark-like outer layers. It is much heavier and harder than normal wood and will not burn. Commonly found in sedimentary basins worldwide.

Identified on: 5/20/2026

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