sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and colors ranging from white to gray and brown.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and colors ranging from white to gray and brown.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or accumulation of siliceous skeletal remains in marine environments.
Uses & applications
Historically used for making stone tools and weapons due to its sharp edges when fractured; occasionally used for decorative landscaping and lapidary work.
Geological facts
Chert was one of the primary materials used by prehistoric humans for knapping arrowheads and blades because of its predictable conchoidal fracture.
Field identification & locations
Identify by its extreme hardness, waxy luster, and sharp conchoidal break edges. Commonly found in limestone and chalk 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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Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
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