mineral

Petrified Wood

Silicified Wood (SiO2)

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-brown, and grey bands; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific Gravity: 2.6-2.9

Hardness: 6
Color: Brown, tan, reddish-brown, and grey bands
Luster: Waxy to vitreous

Identified June 11, 2026More mineral →

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Physical properties

Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-brown, and grey bands; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Specific Gravity: 2.6-2.9

Formation & geological history

Formed through permineralization where organic wood is replaced by silica/chalcedony over millions of years (often Mesozoic or Cenozoic eras) in anaerobic conditions buried under sediment or volcanic ash.

Uses & applications

Used primarily for lapidary work, jewelry (cabochons), ornamental display pieces, furniture accents (tabletops), and as highly sought-after geological collectibles.

Geological facts

Petrified wood is the state fossil of Arizona. While it looks like wood, it is actually a stone cast where the cellular structure of the original tree is sometimes preserved in exquisite detail.

Field identification & locations

Identify by looking for distinct 'growth rings' or bark-like textures on a stone that is too hard to be scratched by a steel knife. Commonly found in riverbeds, volcanic regions, and badlands.