Petrified Wood

Physical Properties

Hardness: 6.5–7.0 (Mohs scale); Color: Brown, grey, tan, and black with visible wood grain; Luster: Vitreous to waxy; Crystal Structure: Amorphous or Cryptocrystalline (Microcrystalline quartz); Cleavage: None; Specific Gravity: 2.6–2.9

Formation & Geological History

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while retaining the original anatomy. This specimen likely dates back to the Triassic to Eocene periods (approx. 50-200 million years ago) and formed in fluvial or volcanic ash environments.

Uses & Applications

Used primarily for decorative objects, jewelry (cabochons), interior design (tabletops), and as astronomical/geological collection specimens.

Geological Facts

Petrified wood is the state fossil of several US states, including Arizona and Washington. The cell structure of the original wood is often so perfectly preserved that it can be examined under a microscope to identify the specific tree species.

Field Identification & Locations

Identify in the field by looking for distinct bark patterns, growth rings, or wood-like textures in a rock that is heavy and dense. It will easily scratch glass but cannot be scratched by a steel knife. Common in the Western US, Madagascar, and Indonesia.

Identified on: 4/28/2026

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