sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, opaque to translucent colors including tan, brown, and grey.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, opaque to translucent colors including tan, brown, and grey.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous microfossil remains in marine environments.
Uses & applications
Historically used for making stone tools, arrowheads, and spark-producing fire-starters; currently utilized in aggregate and abrasives.
Geological facts
Chert fractures with extremely sharp edges, making it one of the preferred materials for prehistoric primitive weaponry.
Field identification & locations
Identify in the field by its distinct conchoidal fracture and high hardness that scratches glass; commonly found embedded in limestone or chalk 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)
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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)
sedimentary