metamorphic
Petrified Wood
Silicified wood (primarily Silicon Dioxide, SiO2)
Hardness: 6.5–7 on Mohs scale; Color: Brown, tan, and grey banding; Luster: Dull to waxy; Structure: Maintains original cellular structure of wood; Specific Gravity: 2.6–2.9
- Hardness
- 6
- Color
- Brown, tan, and grey banding
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5–7 on Mohs scale; Color: Brown, tan, and grey banding; Luster: Dull to waxy; Structure: Maintains original cellular structure of wood; Specific Gravity: 2.6–2.9
Formation & geological history
Formed through permineralization where organic wood is replaced by minerals, typically silica, in anaerobic conditions under volcanic ash or sediment layers. Ranges from 20 to 300 million years old.
Uses & applications
Used for decorative ornaments, jewelry (cabochons), furniture tops, and as geological collectibles.
Geological facts
Famous for forming 'petrified forests' like the one in Arizona (Chinle Formation); it is the state gemstone of Washington and the state rock of Mississippi.
Field identification & locations
Identify in the field by looking for bark-like textures or growth rings in stone. Commonly found in areas with historic volcanic activity and sedimentary basins. Collectors should look for high-contrast colors and intact structural details.
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