fossil
Petrified Wood
Silicified Wood (primarily Quartz/Chalcedony, SiO2)
Hardness: 6.5-7.0 (Mohs scale); Color: Brown, grey, tan with wood-grain textures; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brown, grey, tan with wood-grain textures
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7.0 (Mohs scale); Color: Brown, grey, tan with wood-grain textures; Luster: Vitreous to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through permineralization where organic wood material is replaced by minerals, typically silica from volcanic ash, over millions of years (often Triassic to Eocene epochs) in anaerobic conditions.
Uses & applications
Used in home decor, jewelry (cabochons), lapidary art, and as educational/collector specimens.
Geological facts
Petrified wood is the state fossil of several US states, including Arizona and Washington. It preserves the cellular structure of the original tree so well that growth rings and bark can often be identified.
Field identification & locations
Identify by looking for characteristic wood-like grain, knots, and bark patterns in a stone that is much heavier and harder than wood. Frequently found in badlands and areas with ancient volcanic activity.
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