mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5–7 on Mohs scale; Color: typically shades of brown, grey, red, and yellow; Luster: waxy to vitreous; Crystal structure: Trigonal/Amorphous (microcrystalline Quartz/Chalcedony); Cleavage: none (conchoidal fracture).

Hardness: 6
Color: typically shades of brown, grey, red, and yellow
Luster: waxy to vitreous

Identified March 24, 2026More mineral →

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Physical properties

Formation & geological history

Formed through permineralization over millions of years (commonly Carboniferous to Triassic periods). Organic matter is replaced by minerals, typically quartz, after being buried by sediment or volcanic ash in anaerobic conditions.

Uses & applications

Used in high-end jewelry, lapidary arts (cabochons), interior home decor items like bookends and table tops, and as museum-quality display specimens.

Geological facts

In many specimens, like the one shown, the original bark texture and cellular structure (growth rings) are perfectly preserved in stone. Arizona's Petrified Forest National Park contains one of the world's largest concentrations.

Field identification & locations

Identify in the field by looking for bark-like exterior textures on heavy, stone-like cylinders. Cross-sections often reveal concentric growth rings. Common in areas with ancient fluvial deposits or volcanic ash beds.