metamorphic
Petrified Wood
Silicified wood (primarily SiO2 - Silicon Dioxide/Quartz)
Hardness: 6.5-7 on Mohs scale; Color: Red, brown, orange (due to iron oxides); Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None, conchoidal fracture
- Hardness
- 6
- Color
- Red, brown, orange (due to iron oxides)
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Red, brown, orange (due to iron oxides); Luster: Vitreous to waxy; Crystal structure: Cryptocrystalline; Cleavage: None, conchoidal fracture
Formation & geological history
Formed when plant material is buried by sediment and protected from decay by organisms and oxygen. Groundwater rich in dissolved solids flows through the sediment, replacing original plant material with silica, calcite, or pyrite. Often associated with the Triassic to Eocene periods.
Uses & applications
Used primarily for lapidary work, jewelry, decorative ornaments, furniture (tabletops), and highly valued as mineral specimens for collectors.
Geological facts
In petrified wood, the organic matter is replaced by minerals while maintaining the original structure of the wood tissue, sometimes down to the microscopic cellular level. The Arizona Petrified Forest is one of the world's most famous locations.
Field identification & locations
Identify in the field by looking for bark-like textures on the exterior and growth ring patterns on the cross-sections. It is much heavier than normal wood and cool to the touch. Commonly found in sedimentary basins.
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