fossil

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Cream, tan, brown, beige; Luster: Waxy to vitreous; Crystal structure: Microcrystalline quartz/Chalcedony; Specific gravity: 2.6-2.9

Hardness: 6
Color: Cream, tan, brown, beige
Luster: Waxy to vitreous

Identified July 21, 2026More fossil →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Cream, tan, brown, beige; Luster: Waxy to vitreous; Crystal structure: Microcrystalline quartz/Chalcedony; Specific gravity: 2.6-2.9

Formation & geological history

Formed through permineralization over millions of years (often Triassic to Miocene), where organic wood cells are replaced by silica from groundwater in an anaerobic environment, usually after burial by volcanic ash or river sediments.

Uses & applications

Used for decorative lapidary work, jewelry (cabochons), interior design (bookends, tabletops), and as geological teaching specimens.

Geological facts

Arizona's Petrified Forest National Park contains some of the world's most famous deposits. While it looks like wood, it is entirely stone, often preserving microscopic cellular details of the original tree.

Field identification & locations

Identify by looking for wood-like grain patterns, tree rings, or bark textures in a heavy, cold-to-the-touch stone specimen. Commonly found in sedimentary basins and areas with historical volcanic activity.