metamorphic
Petrified Wood
Silicified Wood (primarily SiO2)
Hardness: 6.5–7 on Mohs scale. Color: Tan, beige, brown, and cream with visible grain. Luster: Vitreous to dull. Structure: Microcrystalline silica (Chalcedony/Quartz). Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Tan, beige, brown, and cream with visible grain
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5–7 on Mohs scale. Color: Tan, beige, brown, and cream with visible grain. Luster: Vitreous to dull. Structure: Microcrystalline silica (Chalcedony/Quartz). Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through permineralization where organic wood materials are replaced by silica (quartz) from groundwater while buried under sediment or volcanic ash. This specimen likely dates from the Paleozoic to Cenozoic eras.
Uses & applications
Used primarily for ornamental jewelry (cabochons), interior decor (bookends, tabletops), and as geological teaching specimens.
Geological facts
In petrified wood, the original cellular structure of the wood is often preserved in stone, allowing paleobotanists to identify the specific ancient tree species. It is the state gemstone of Washington and Arizona.
Field identification & locations
Identify in the field by looking for bark-like textures or growth rings on stones that feel significantly heavier and harder than wood. Commonly found in sedimentary basins and areas of historic volcanic activity like the American Southwest.
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