sedimentary
Chert (Jasper/Flint variety)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and cream with iron staining. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.65.
- Hardness
- 6
- Color
- Tan, brown, and cream with iron staining
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 on Mohs scale. Color: Tan, brown, and cream with iron staining. Luster: Dull to waxy. Structure: Cryptocrystalline. Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.65.
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation within sedimentary rock layers like limestone. This specimen shows significant river-worn weathering.
Uses & applications
Historically used for stone tools and weapons due to its sharp edges when fractured. Currently used in road construction, landscaping, and lapidary work.
Geological facts
Chert is incredibly durable and resistant to chemical weathering, which is why it often persists in riverbeds long after surrounding limestone has eroded away.
Field identification & locations
Identify by its hardness (it will scratch glass) and its smooth, shell-like (conchoidal) fracture pattern where chips have been taken out. Commonly found in gravel pits and stream beds.
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