metamorphic
Petrified Wood
Silicified wood (primarily Silicon Dioxide - SiO2)
Hardness: 6.5-7 (Mohs scale), Color: tan, cream, beige, and brown with visible wood grain patterns, Luster: waxy to vitreous, Crystal structure: cryptocrystalline quartz, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.9.
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (Mohs scale), Color: tan, cream, beige, and brown with visible wood grain patterns, Luster: waxy to vitreous, Crystal structure: cryptocrystalline quartz, Cleavage: none (conchoidal fracture), Specific Gravity: 2.6-2.9.
Formation & geological history
Formed when plant material is buried by sediment and protected from decay. Over millions of years (often during the Mesozoic or Cenozoic eras), groundwater rich in dissolved silica flows through the sediment, replacing the organic plant cells with minerals while preserving the original wood structure.
Uses & applications
Used primarily for ornamental purposes, jewelry (cabochons), interior design (tables, bookends), and as educational fossils.
Geological facts
Petrified wood can retain such microscopic detail that the original tree's species can often be identified. Entire forests, like the Petrified Forest National Park in Arizona, have been preserved this way.
Field identification & locations
Identify in the field by looking for 'rock logs' that feature bark textures, tree rings, or cellular wood grain patterns. It will feel much heavier than wood and cannot be scratched by a steel knife.
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