sedimentary
Petrified Wood
Silicified Wood (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and dark grey. Luster: Dull to waxy. Crystal structure: Microcrystalline quartz (chalcedony/opal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.9.
- Hardness
- 6
- Color
- Brown, tan, and dark grey
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Brown, tan, and dark grey. Luster: Dull to waxy. Crystal structure: Microcrystalline quartz (chalcedony/opal). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.9.
Formation & geological history
Formation through permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic conditions under sediment. This often occurred millions of years ago in volcanic or fluvial environments.
Uses & applications
Ornamental jewelry, lapidary art, decorative bookends, and popular geological collecting specimens. Large slabs are used for furniture.
Geological facts
Unlike typical fossils, petrified wood is a three-dimensional representation of the original organic material. Some specimens retain perfectly visible tree rings and bark textures.
Field identification & locations
Identify by looking for wood-like grain patterns, bark textures, or growth rings in a heavy, stony material. Commonly found in areas with high ancient volcanic activity or arid badlands.
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