sedimentary
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Tans, browns, and grays (often with multi-colored minerals); Luster: Dull to waxy/vitreous; Crystal structure: Trigonal/Cryptocrystalline (replaces organic cellular structure); Specific Gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Tans, browns, and grays (often with multi-colored minerals)
- Luster
- Dull to waxy/vitreous
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Tans, browns, and grays (often with multi-colored minerals); Luster: Dull to waxy/vitreous; Crystal structure: Trigonal/Cryptocrystalline (replaces organic cellular structure); Specific Gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization, a process where organic material is replaced by minerals (usually silica) in an anaerobic environment. This typically occurs when wood is buried under volcanic ash or sedimentary flow. Specimens range from 20 million to 300 million years old.
Uses & applications
Used in lapidary arts for jewelry (cabochons), interior design (tabletops, bookends), and as highly sought-after display specimens for fossil and mineral collectors.
Geological facts
In some cases, petrified wood preserves the original cellular structure of the tree so perfectly that microscopic cell walls and tree rings can be identified. The Petrified Forest National Park in Arizona contains one of the world's largest concentrations of this material.
Field identification & locations
Identify in the field by looking for a characteristic bark-like texture and wood grain patterns on a heavy, stone-like object. It will be much harder than real wood and cannot be scratched by a steel knife. Common in the Western United States, Madagascar, and Indonesia.
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