sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness 7 on the Mohs scale, typically pale green, grey, or white with a waxy to dull luster and conchoidal fracture.
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Physical properties
Hardness 7 on the Mohs scale, typically pale green, grey, or white with a waxy to dull luster and conchoidal fracture.
Formation & geological history
Formed through the chemical precipitation of silica from seawater or the replacement of limestone by silica-rich solutions.
Uses & applications
Historically used for making stone tools and weapons due to its sharp conchoidal fracture, and occasionally used in landscaping or lapidary work.
Geological facts
Chert breaks with sharp edges similar to glass, making it one of the most reliable materials for ancient arrowheads and blades.
Field identification & locations
Identified by its extreme hardness, conchoidal fracture, and lack of reaction to acid. Commonly found within chalk and limestone formations worldwide.
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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
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Sandstone or Siltstone
Arenite (if sandstone)
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Sandstone
Arenite
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Shale
Shale (clastic sedimentary rock)
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Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
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