sedimentary
Petrified Wood
Silicified Wood (primarily SiO2)
Hardness: 6.5-7 (Mohs); Color: Red, brown, tan, and grey due to iron and manganese; Luster: Vitreous to dull; Structure: Cryptocrystalline; Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Red, brown, tan, and grey due to iron and manganese
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs); Color: Red, brown, tan, and grey due to iron and manganese; Luster: Vitreous to dull; Structure: Cryptocrystalline; Specific Gravity: 2.6-2.9
Formation & geological history
Formed via permineralization where organic wood materials are replaced by minerals (usually silica) in anaerobic conditions over millions of years, often dating to the Triassic or Jurassic periods.
Uses & applications
Used in jewelry (cabochons), interior decor (tabletops, bookends), and highly valued as geological collector specimens.
Geological facts
Arizona's Petrified Forest National Park contains wood that is approximately 225 million years old. The colors are determined by trace elements: red/orange from hematite and yellow from limonite.
Field identification & locations
Identify in the field by looking for distinct bark-like textures and growth rings on a stone that is much harder than typical sedimentary rock. Common in arid badlands and volcanic ash deposits.
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