metamorphic
Agatized Petrified Wood
Silicon Dioxide (SiO2) - Chalcedony pseudomorph after Wood
Hardness: 6.5-7 (Mohs scale); Color: Variegated levels of brown, tan, blue-grey, and red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.
- Hardness
- 6
- Color
- Variegated levels of brown, tan, blue-grey, and red
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Variegated levels of brown, tan, blue-grey, and red; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None; Specific Gravity: 2.58-2.64.
Formation & geological history
Formed through permineralization over millions of years (typically Triassic to Cenozoic). Organic matter is replaced by silica-rich groundwater in anaerobic conditions, preserving the original cellular structure of the wood.
Uses & applications
Used in ornamental jewelry (cabochons), interior decor (bookends, tabletops), and as prized specimens for geological collectors.
Geological facts
Petrified wood is the state mineral of Washington and Mississippi and the state rock of Arizona. It takes nearly 100 million years for some forests to fully silicify.
Field identification & locations
Identify by looking for preserved wood grain, bark textures, or annual rings under magnification despite being solid stone. Commonly found in Arizona (USA), Madagascar, and Indonesia. Collectors look for high polish and vibrant color contrast.
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