sedimentary
Petrified Wood
Silicified wood (Quartz/Chalcedony/Opal)
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-pink, grey; Luster: Vitreous to waxy; Structure: Retains cellular structure of original wood; Cleavage: None (conchoidal fracture); Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Brown, tan, reddish-pink, grey
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brown, tan, reddish-pink, grey; Luster: Vitreous to waxy; Structure: Retains cellular structure of original wood; Cleavage: None (conchoidal fracture); Gravity: 2.6-2.9
Formation & geological history
Formed through permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic conditions, often under volcanic ash or sediment layers. Most specimens are 20 to 200 million years old.
Uses & applications
Used for ornamental furniture, jewelry (cabochons), lapidary art, aquarium decor, and high-value geological collections.
Geological facts
The word 'petrified' comes from the Greek root 'petro,' meaning rock. Entire forests, like the one in Arizona (Petrified Forest National Park), have been preserved this way since the Triassic period.
Field identification & locations
Identify by visible bark-like textures or growth rings combined with the weight and hardness of stone. Found in various global locations including the USA, Argentina, Egypt, and Indonesia.
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