Petrified Wood

Physical Properties

Hardness: 6.5-7 (Mohs scale); Color: Variegated shades of brown, grey, black, and white; Luster: Vitreous to waxy; Crystal structure: Microcrystalline/Cryptocrystalline; 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 (typically Mesozoic or Cenozoic era), groundwater rich in dissolved solids flows through the sediment, replacing organic material with silica (chalcedony or opal).

Uses & Applications

Used primarily for landscaping, interior design (bookends, tabletops), jewelry making (cabochons), and as museum or private geological specimens.

Geological Facts

Petrified wood is the state fossil of Arizona. In some cases, the mineralization is so precise that cellular structures and tree rings remain perfectly visible under a microscope.

Field Identification & Locations

Identify in the field by looking for bark-like textures on the exterior and a conchoidal (glassy) fracture pattern on broken surfaces. Often found in badlands or areas with volcanic ash deposits like the Petrified Forest National Park.

Identified on: 4/14/2026

Mode: Standard