metamorphic
Petrified Wood
Silicified Wood (primarily SiO₂ - Silicon Dioxide)
Hardness: 6.5–7 on Mohs scale. Color: Grey, brown, and tan with woody textures. Luster: Vitreous to dull. Crystal structure: Hexagonal (cryptocrystalline quartz). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Grey, brown, and tan with woody textures
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Grey, brown, and tan with woody textures. Luster: Vitreous to dull. Crystal structure: Hexagonal (cryptocrystalline quartz). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6–2.9.
Formation & geological history
Formed via permineralization, where organic wood material is replaced by minerals (usually silica) while buried under sediment. Often dates to the Triassic, Jurassic, or Cenozoic eras (approx. 20–250 million years old).
Uses & applications
Used for ornamental furniture (tabletops), jewelry (cabbing), home decor, and educational/scientific study in paleontology.
Geological facts
Petrified wood is the state gem of Washington and the state fossil of Arizona. Famous specimens are found in the Petrified Forest National Park, where trees fallen millions of years ago were preserved by volcanic ash.
Field identification & locations
Identify in the field by looking for distinct bark-like textures or growth rings on stones that feel significantly heavier and harder than wood. Frequently found in riverbeds or areas with historic volcanic activity.
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