sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and typically brown, grey, or tan in color.
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Physical properties
Hardness of 7 on the Mohs scale, waxy luster, conchoidal fracture, and typically brown, grey, or tan in color.
Formation & geological history
Formed through the chemical precipitation of silica from seawater or the accumulation of siliceous microfossil skeletons during the Paleozoic and Mesozoic eras.
Uses & applications
Historically used for making stone tools and arrowheads due to its sharp conchoidal fracture; currently used as aggregate and in abrasive products.
Geological facts
Also commonly known as flint when dark-colored, chert was a primary material for early human toolmaking and starting fires with steel.
Field identification & locations
Identify in the field by its hardness (scratches glass), waxy or dull luster, and sharp-edged conchoidal breaking pattern. Found worldwide in limestone formations.
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Other sedimentary specimens
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
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary