sedimentary
Petrified Wood (Jet or Coalified Wood appearance)
Silicified wood (principally SiO2) or Carbonized Wood
Hardness: 6.5-7 (if silicified), Color: Black to dark brown, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Specific Gravity: 2.5-2.8
- Hardness
- 6
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Physical properties
Hardness: 6.5-7 (if silicified), Color: Black to dark brown, Luster: Waxy to dull, Crystal structure: Cryptocrystalline, Specific Gravity: 2.5-2.8
Formation & geological history
Formed when plant material is buried by sediment and protected from decay by oxygen. Groundwater rich in dissolved solids flows through the sediment, replacing the original plant material with mineral matter over millions of years.
Uses & applications
Used primarily for decorative objects, lapidary arts, jewelry, and as a geological collecting specimen.
Geological facts
Black petrified wood often gains its color from the presence of carbon or manganese oxides during the permineralization process. Entire fossilized forests exist where trees were buried by volcanic ash.
Field identification & locations
Identify by looking for visible grain or bark textures preserved in stone. Common in the Western United States (Arizona, Utah). Collectors should check for high density and distinct wood-like fractures.
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