sedimentary
Chert (and Flint)
Chert (SiO2)
Hardness: 7 (Mohs scale), Color: tan, grey, brown, or white; Luster: waxy to dull; Structure: microcrystalline quartz; Cleavage: none, exhibits conchoidal fracture
- Hardness
- 7 (Mohs scale), Color: tan, grey, brown, or white
- Color
- tan, grey, brown, or white
- Luster
- waxy to dull
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, brown, or white; Luster: waxy to dull; Structure: microcrystalline quartz; Cleavage: none, exhibits conchoidal fracture
Formation & geological history
Formed through the accumulation of silica-rich organic remains (like diatoms or radiolaria) or chemical precipitation in marine environments; age varies from Precambrian to Cenozoic.
Uses & applications
Historically used for stone tools and arrowheads; currently used in construction aggregate and road surfacing.
Geological facts
Flint is a variety of chert that was essential for early humans to create 'fire-starting' sparks and sharp blades; it is incredibly durable and chemically stable.
Field identification & locations
Identify by its 'shell-like' conchoidal fractures and ability to scratch glass. Commonly found in limestone or chalk beds as nodules.
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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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Sandstone Grain
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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