sedimentary
Petrified Wood
Silicified Wood (primarily Chalcedony or Quartz, SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Gray, brown, white, tan. Luster: Vitreous to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None, conchoidal fracture.
- Hardness
- 6
- Color
- Gray, brown, white, tan
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Gray, brown, white, tan. Luster: Vitreous to dull. Crystal Structure: Hexagonal (cryptocrystalline). Cleavage: None, conchoidal fracture.
Formation & geological history
Formed through permineralization where organic plant matter is replaced by minerals, typically silica from volcanic ash, over millions of years (commonly Carboniferous to Cenozoic eras) in anaerobic environments.
Uses & applications
Used in jewelry (lapidary), decorative ornaments, furniture tops, and as educational/collector specimens.
Geological facts
Petrified wood is the state fossil of Washington and several other US states. Most specimens contain the original cell structure of the tree perfectly preserved in stone.
Field identification & locations
Identify by looking for bark-like textures, growth rings, and woody grain patterns on a rock that feels much heavier and harder than actual wood. Found in areas with historic volcanic activity and river basins.
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