sedimentary
Chert (Jasper variation)
Microcrystalline Quartz (SiO2)
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to earthy orange with grey streaks; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture).
- Hardness
- 6
- Color
- Brownish-red to earthy orange with grey streaks
- Luster
- Dull to waxy
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Brownish-red to earthy orange with grey streaks; Luster: Dull to waxy; Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture).
Formation & geological history
Forms through the accumulation of silica-rich microfossils on the seafloor or through the replacement of limestone. This specimen appears water-worn, likely from a fluvial (river) environment.
Uses & applications
Historically used for stone tools due to sharp edges; currently used for lapidary work, jewelry, and as decorative gravel.
Geological facts
Chert is so durable that it often survives long-term erosion, often found as smooth pebbles in riverbeds far from its source rock. Red versions are often called Jasper.
Field identification & locations
Identify by its hardness (it will scratch glass) and its smooth, waxy feel when wet. Found globally in sedimentary basins. Look for smooth, rounded shapes in stream beds.
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