Petrified Wood

Physical Properties

Hardness: 6.5–7 on Mohs scale; Color: Tan, brown, yellow-orange; Luster: Waxy to vitreous; Crystal structure: Hexagonal/Microcrystalline (Quartz); Cleavage: None; Specific Gravity: 2.6–2.9.

Formation & Geological History

Formed when plant material is buried by sediment and protected from decay by oxygen and organisms. Over millions of years, mineral-rich water flows through the sediment, replacing original plant tissues with silica (quartz) or opal. Most specimens date from the Mesozoic Era.

Uses & Applications

Used primarily for lapidary work, jewelry (cabochons), interior decoration, and as a popular collector's item in natural history museums and private collections.

Geological Facts

Petrified wood is a fossil in which the organic remains have been replaced by minerals in the slow process of permineralization. Arizona's Petrified Forest National Park contains one of the world's largest and most colorful concentrations of petrified wood.

Field Identification & Locations

Identify in the field by looking for wood-like grain patterns, knots, or bark textures in a material that feels like stone and cannot be scratched by a steel knife. Commonly found in sedimentary basins worldwide.

Identified on: 4/22/2026

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