sedimentary
Chert (containing a small fossil)
Microcrystalline Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, and gray; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, and gray
- Luster
- Waxy to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, and gray; Luster: Waxy to dull; Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed from the precipitation of silica-rich fluids or the accumulation of siliceous skeletal remains (like diatoms or radiolaria) in marine environments. This specimen appears to contain a small fossilized shell fragment or impression.
Uses & applications
Historically used for making stone tools (arrowheads/scrapers) due to its conchoidal fracture. Modernly used in road construction as aggregate or as decorative stones.
Geological facts
Chert is extremely durable and can survive long periods of weathering. Because it forms in marine environments, it frequently traps fossils of microscopic or small marine organisms.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel nail) and the way it breaks into smooth, curved surfaces (conchoidal fracture). It often has a waxy feel similar to flint.
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