metamorphic
Petrified Wood (Silicified Wood)
Silicified Paleoflora (mainly Quartz, SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, white, and orange-red (due to iron oxides); Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None; Specific gravity: 2.6–2.9.
- Hardness
- 6
- Color
- Brown, tan, white, and orange-red (due to iron oxides)
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, tan, white, and orange-red (due to iron oxides); Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None; Specific gravity: 2.6–2.9.
Formation & geological history
Formed when plant material is buried by sediment (often volcanic ash) and permineralized. Over millions of years, silica-rich groundwater replaces the organic cell structure with minerals. This specimen likely dates from the Mesozoic or Cenozoic eras.
Uses & applications
Used for lapidary work (jewelry, bookends, tabletops), decorative landscaping, and as educational/collector museum pieces.
Geological facts
Petrified wood is the state fossil of Arizona, North Dakota, and Louisiana. Despite being made of stone, the internal structure can sometimes preserve tree rings and cell details visible under a microscope.
Field identification & locations
Identify by looking for wood-like textures (bark patterns, grain, knots) combined with the extreme hardness and weight of stone. Often found in badlands or areas with ancient sedimentary deposits.
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