sedimentary
Chert (and Petrified Wood)
Silicon Dioxide (SiO2)
Hardness: 7.0 (Mohs). Color: Tan, white, and translucent gray. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
- Hardness
- 7
- Color
- Tan, white, and translucent gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7.0 (Mohs). Color: Tan, white, and translucent gray. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific gravity: 2.65.
Formation & geological history
Formed through the replacement of organic material (likely wood fiber) by silica-rich groundwater. This specimen displays a fibrous/woody texture indicative of permineralization, typically occurring in ancient volcanic ash or fluvial deposits.
Uses & applications
Historically used for stone tools due to its sharp edges. Today used in landscape decor, lapidary arts, and as geological collector specimens.
Geological facts
This specimen appears to be a fragment of petrified wood consisting of chert/chalcedony. It preserves the original cellular structure of the plant while being completely replaced by minerals over millions of years.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy feel, and the preservation of fibrous or grain-like patterns reminiscent of wood. Commonly found in areas with historic volcanic activity or sedimentary basins like the Petrified Forest in Arizona.
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