sedimentary
Petrified Wood
Silicified Wood (primarily SiO2 - Silicon Dioxide)
Hardness: 6.5–7 Mohs; Color: Red, brown, orange, and gray due to iron and manganese impurities; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5–7 Mohs; Color: Red, brown, orange, and gray due to iron and manganese impurities; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6–2.9
Formation & geological history
Formed through permineralization, where organic wood material is replaced by silica-rich groundwater while being buried under sediment, often volcanic ash, originating from the Triassic period (approx. 200 million years ago) or later.
Uses & applications
Used primarily for lapidary work, jewelry (cabochons), ornamental furniture (tabletops), and as highly collectible geological display specimens.
Geological facts
Famous locations include the Petrified Forest National Park in Arizona; it is the state fossil of Arizona and is essentially a three-dimensional stone representation of an ancient tree.
Field identification & locations
Identify in the field by looking for stone specimens that retain the visual texture of wood grain, bark patterns, or growth rings. Common in badlands and areas with ancient river deposits.
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