sedimentary

Petrified Wood

Silicified Wood (primarily Chalcedony/Quartz, SiO2)

Hardness: 6.5-7 on Mohs scale; Color: Multi-colored (reds, yellows, browns, blacks) due to impurities like iron and manganese; Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.9.

Hardness: 6
Luster: Vitreous to waxy

Identified May 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization, a process where organic material is replaced by minerals (usually silica) while maintaining the original cellular structure. Many specimens date back to the Triassic period (approx. 225 million years ago).

Uses & applications

Used in lapidary arts for jewelry, bookends, furniture (tabletops), and as decorative museum or collector specimens.

Geological facts

The vibrant colors are caused by trace elements: iron creates reds and yellows, manganese creates pinks and oranges, and carbon/copper creates blacks and greens. The Petrified Forest National Park in Arizona is one of the most famous locations globally.

Field identification & locations

Identify by looking for preserved wood grain, growth rings, or bark textures on the exterior. It feels much heavier than modern wood and can be found in areas with ancient volcanic ash deposits. Common in Arizona, Madagascar, and Indonesia.

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