mineral

Petrified Wood

Silicified Wood (primarily SiO2)

Hardness: 6.5-7 (Mohs); Color: Brown, tan, cream, and grey with wood-grain patterns; Luster: Vitreous to waxy after polishing; Crystal system: Hexagonal (cryptocrystalline); Specific gravity: 2.6-2.9.

Hardness: 6
Color: Brown, tan, cream, and grey with wood-grain patterns
Luster: Vitreous to waxy after polishing

Identified June 17, 2026More mineral →

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Physical properties

Formation & geological history

Formed via permineralization where organic matter is replaced by silica (chalcedony/quartz) over millions of years. This specimen likely dates back to the Triassic or Cenozoic periods, formed in anaerobic conditions under volcanic ash or sedimentary layers.

Uses & applications

Used primarily for decorative objects like bookends, tabletops, and jewelry. It is a highly valued collector's item for display and educational purposes.

Geological facts

Petrified wood is the state fossil of Washington and Arizona. Entire ancient forests exist as stone, such as those in the Petrified Forest National Park in Arizona, which contains wood that is over 200 million years old.

Field identification & locations

Identify by looking for preserved plant structures like bark, tree rings, and wood grain in a piece that feels heavy and cold like stone. Found in various regions including the USA, Madagascar, and Indonesia.