sedimentary
Chert (Flint)
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 7 (Mohs scale), Color: tan, grey, or brown, Luster: waxy to dull, Structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, grey, or brown, Luster: waxy to dull, Structure: microcrystalline, Cleavage: none (conchoidal fracture), Specific Gravity: 2.65
Formation & geological history
Formed through the accumulation of silica-rich organic remains or chemical precipitation in marine environments; commonly found in limestone or chalk beds.
Uses & applications
Used historically for stone tools and weapons (arrowheads), as a fire-starter, and currently in construction aggregate or as a lapidary material.
Geological facts
Chert is so hard it can scratch steel. The sharp edges created by its conchoidal fracture made it the premier material for prehistoric toolmaking globally.
Field identification & locations
Look for a smooth, waxy surface and shell-like (conchoidal) fractures. Often found as nodules or layers within sedimentary rock formations.
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Fossil-bearing concretion, possibly containing a fossil shell or other organic inclusion
Calcareous concretion; exact fossil and host-rock composition are not identifiable from the image
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Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
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Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary