metamorphic
Petrified Wood
Silicified Wood (primarily SiO₂ - Silicon Dioxide)
Hardness: 6.5–7 on Mohs scale; Color: Reddish-brown, orange, and tan (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Cryptocrystalline (chalcedony/quartz replaces organic matter); Specific Gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Reddish-brown, orange, and tan (due to iron oxides)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Reddish-brown, orange, and tan (due to iron oxides); Luster: Vitreous to dull; Crystal structure: Cryptocrystalline (chalcedony/quartz replaces organic matter); Specific Gravity: 2.6–2.9.
Formation & geological history
Formed through permineralization when woody plant matter is buried under sediment or volcanic ash. Over millions of years (often Triassic to Eocene epochs), mineral-rich groundwater replaces organic cells with silica. Geological age varies but commonly ranges from 20 to 200 million years old.
Uses & applications
Used in high-end furniture (slabs), decorative home decor, lapidary arts like cabochons for jewelry, and as a popular specimen for geological collections.
Geological facts
Arizona's Petrified Forest National Park contains one of the world's largest concentrations of petrified wood. While it looks like wood, it is actually a fossil composed entirely of stone, often preserving the microscopic cellular structure of the original tree.
Field identification & locations
Identify by looking for distinctive bark-like textures on the exterior and growth ring patterns on cross-sections. Common in arid sedimentary basins. Tip: check for a 'conchoidal' (glass-like) fracture pattern which distinguishes it from modern rotting wood.
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