sedimentary
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, red, and grey; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Chalcedony/Quartz); Specific gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Brown, tan, red, and grey
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, red, and grey; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Chalcedony/Quartz); Specific gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (primarily silica) over millions of years, often in volcanic ash or river sedimentary environments during the Triassic to Cenozoic eras.
Uses & applications
Used for lapidary work, jewelry (cabochons), ornamental furniture, bookends, and as a popular geological collectible.
Geological facts
Arizona's Petrified Forest National Park contains one of the world's largest concentrations of petrified wood. It is essentially a fossil that has been completely turned to stone.
Field identification & locations
Identify in the field by looking for bark-like textures, growth rings, and wood grain preserved in stone. Common in areas with history of volcanic activity and ancient riverbeds.
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