fossil
Petrified Wood
Silicified Wood (primarily Chalcedony/Quartz, SiO2)
Hardness: 6.5–7 (Mohs scale); Color: Brown, gray, tan, or black with visible wood grain; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brown, gray, tan, or black with visible wood grain
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 (Mohs scale); Color: Brown, gray, tan, or black with visible wood grain; Luster: Dull to waxy; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through permineralization, where organic wood material is replaced by silica (quartz) from groundwater over millions of years, typically in volcanic ash or sedimentary environments.
Uses & applications
Used in lapidary work for cabochons, interior decor (bookends, tables), and highly valued by fossil and mineral collectors.
Geological facts
Petrified wood can preserve the original cellular structure of the tree so perfectly that individual species can often be identified. Some specimens are up to 200 million years old.
Field identification & locations
Identify in the field by looking for 'rock-like' weight combined with bark textures, growth rings, or wood fibers. Found globally, notably in Arizona (USA), Madagascar, and Indonesia.
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