sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, and typically gray, white, or brown in color.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, conchoidal fracture, and typically gray, white, or brown in color.
Formation & geological history
Formed via the chemical precipitation of silica from seawater or the accumulation of siliceous microfossil remains over millions of years.
Uses & applications
Historically used for making stone tools and arrowheads due to its sharp conchoidal fracture; occasionally used in decorative landscaping or lapidary work.
Geological facts
Chert includes varieties like flint and jasper, and prehistoric humans prized it for its ability to be chipped into extremely sharp edges.
Field identification & locations
Identify it by its extreme hardness, waxy luster, and smooth conchoidal fracture surfaces; it is commonly found nodules within limestone 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
fossil
Fossiliferous Sedimentary Rock
Sedimentary limestone with invertebrate fossil imprint
fossil
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite
sedimentary
Shale
Shale (clastic sedimentary rock)
sedimentary
Shale (or Mudstone/Siltstone)
Sedimentary Mudrock (SiO2, Al2O3 base with clay minerals)
sedimentary