sedimentary

Petrified Wood

Silicified Wood (primarily SiO2 - Silicon Dioxide)

Hardness: 6.5–7 on Mohs scale; Color: Red, brown, and yellowish due to iron oxides; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline (chalcedony/quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9

Hardness: 6
Color: Red, brown, and yellowish due to iron oxides
Luster: Waxy to vitreous

Identified March 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the process of permineralization where organic wood materials are replaced by silica (quartz) from groundwater while buried in sediment, often occurring over millions of years (commonly from the Triassic or Tertiary periods).

Uses & applications

Used in lapidary work for jewelry (cabochons), ornamental furniture (table tops), bookends, and as educational display specimens for fossil collectors.

Geological facts

In petrified wood, the replacement process is often so precise that the original cell structure and tree rings of the ancient plant are perfectly preserved in stone.

Field identification & locations

Identify in the field by looking for rock specimens with bark-like textures or visible growth rings; commonly found in areas like Arizona (Petrified Forest National Park), Madagascar, and Indonesia.

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