sedimentary
Petrified Wood
Silicified Wood (SiO2 - Silicon Dioxide)
Hardness: 6.5–7 on Mohs scale; Color: Gray, brown, tan, and reddish-orange; Luster: Dull to vitreous; Structure: Microcrystalline (preserving organic cellular structure); Specific Gravity: 2.6–2.9
- Hardness
- 6
- Color
- Gray, brown, tan, and reddish-orange
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Gray, brown, tan, and reddish-orange; Luster: Dull to vitreous; Structure: Microcrystalline (preserving organic cellular structure); Specific Gravity: 2.6–2.9
Formation & geological history
Formed through permineralization where organic remains (wood) are replaced by minerals (usually silica) in subterranean settings. Common in environments with volcanic ash or alluvial deposits over millions of years (often Triassic or Jurassic periods).
Uses & applications
Used in ornamental jewelry (cabochons), interior design (bookends, tabletops), and as a popular educational specimen for geological and paleontological collections.
Geological facts
Petrified wood is the state stone of Washington and the state fossil of Arizona. The cell-by-cell replacement can be so precise that individual growth rings and even cellular structures can be seen under a microscope.
Field identification & locations
Identify in the field by looking for distinct bark-like textures or growth rings on an object that feels significantly heavier than wood and is cold to the touch. Commonly found in arid locations with exposed sedimentary layers like Arizona, Utah, and Wyoming.
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