Petrified Wood

Physical Properties

Hardness: 6.5-7 on Mohs scale; Color: Brown, gray, black, often with reddish or yellowish tones; Luster: Waxy to vitreous (glassy); Crystal Structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None, exhibits conchoidal fracture.

Formation & Geological History

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining original anatomical structure. Commonly occurs in volcanic ash beds or sedimentary deposits where wood is buried rapidly without oxygen. Age ranges from the Devonian to the Pleistocene (hundreds of millions to tens of thousands of years).

Uses & Applications

Used primarily for display specimens, lapidary work (jewelry, cabochons), high-end furniture (tabletops), and as educational items for geology and paleontology.

Geological Facts

The Petrified Forest National Park in Arizona is one of the world's most famous locations. Petrified wood is the state fossil of Washington and the state rock of Mississippi. It can sometimes preserve incredible detail, including bark patterns and individual tree rings.

Field Identification & Locations

Identify by looking for wood-like textures such as grain, growth rings, or bark that has been completely mineralized into stone (it will be heavy and hard, not like wood). Often found in desert badlands or areas with ancient river deposits.

Identified on: 5/20/2026

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