sedimentary
Petrified Wood (Agatized/Silicified Wood)
Silicified Wood / Chalcedony (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Tan, cream, or brown with visible wood-grain patterns; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
- Hardness
- 6
- Color
- Tan, cream, or brown with visible wood-grain patterns
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Tan, cream, or brown with visible wood-grain patterns; Luster: Waxy to vitreous; Crystal structure: Cryptocrystalline (Microcrystalline Quartz); Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.9
Formation & geological history
Formed via permineralization, where organic wood material is replaced by minerals (usually silica) from groundwater while buried in sediment. This process typically occurs over millions of years, often in volcanic ash beds or river floodplains (Triassic to Neogene periods).
Uses & applications
Used in lapidary arts for jewelry, bookends, and decorative furniture. Highly valued as museum-quality display specimens and for teaching paleobotany.
Geological facts
The specimen displays distinctive cellular structural preservation, often called 'agatized' or 'opalized' wood depending on the mineral replacement. The Petrified Forest National Park in Arizona is one of the world's most famous locations for these specimens.
Field identification & locations
Identify in the field by looking for 'bark-like' exterior textures and внутренней wood-grain patterns that remain despite the object being heavy and cold like stone. Found frequently in eroded badlands and gravel pits in the Western United States (Arizona, Oregon, Washington).
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