sedimentary
Chert (Jasper)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)
- Hardness
- 6
- Color
- reddish-brown
- Luster
- waxy to dull
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Physical properties
Hardness: 6.5-7 Mohs; Color: reddish-brown; Luster: waxy to dull; Crystal structure: Microcrystalline/cryptocrystalline; Fractures: Conchoidal (shell-like curves)
Formation & geological history
Formed from the accumulation of silica-rich microfossils or via chemical precipitation within sedimentary rock layers, often associated with iron oxide impurities which give it the dark brown color.
Uses & applications
Historical use for stone tools/arrowheads due to its sharp edges; modern use as gemstones, landscaping rock, and in jewelry (lapidary).
Geological facts
Chert is so durable that it is often found in riverbeds long after the surrounding rock has weathered away. It was a primary material used by prehistoric humans for creating flint tools.
Field identification & locations
Identify by its hardness (will scratch glass) and its smooth, curved conchoidal fractures. Common in limestone formations and gravel deposits worldwide.
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Sedimentary limestone with invertebrate fossil imprint
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Sandstone or Siltstone
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Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
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