mineral

Petrified Wood

Silicified Wood (primarily SiO₂ / Silicon Dioxide)

Hardness: 6.5-7 (Mohs scale), Color: Cream, tan, and light brown with visible wood grain patterns, Luster: Vitreous to waxy, Crystal Structure: Cryptocrystalline (Microcrystalline Quartz), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9

Hardness: 6

Identified March 18, 2026More mineral →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic wood material is replaced by silica-rich minerals (often from volcanic ash) over millions of years. This usually occurs under anaerobic conditions during the Cenozoic or Mesozoic eras.

Uses & applications

Commonly used for lapidary work, jewelry (cabochons), interior design (polished slabs), and as a popular educational geological specimen for collectors.

Geological facts

Petrified wood is essentially a fossil where all organic matter has been replaced with minerals while retaining the original structure of the wood, sometimes down to the cellular level. Arizona's Petrified Forest National Park contains some of the world's most famous deposits.

Field identification & locations

Identify in the field by looking for distinct bark-like textures or growth rings on the exterior of an unusually heavy and hard rock. It will not scratch with a steel knife. Common in regions with high volcanic activity and sedimentary basins like the Western United States.

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