sedimentary
Chert (Jasper/Flint variety)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or brown; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or brown
- Luster
- Dull to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or brown; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline (microscopic quartz); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or via chemical precipitation in marine or groundwater environments. Found in sedimentary layers like limestone or chalk.
Uses & applications
Historically used for stone tools and arrowheads. Currently used in road surfacing, decorative landscaping, and occasionally as a gemstone (Jasper varieties).
Geological facts
Because of its conchoidal fracture, it breaks with sharp edges, making it a primary material for prehistoric 'flint-knapping.' It is incredibly durable and chemically stable.
Field identification & locations
Identify by its extreme hardness (scratches glass), smooth waxy feel on breaks, and 'shell-like' curved fracture patterns. Commonly found in riverbeds or as nodules in limestone outcrops.
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Cone-in-cone structure (Limestone)
Cone-in-cone structure (Secondary Sedimentary Structure)
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Chert Breccia
Brecciated Chert (Microcrystalline Silica)
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Clastic Sedimentary Rock Grain (SiO2 dominated)
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Shale or Slaty Mudstone
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Sandstone
Arenite (primarily SiO2)
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