sedimentary
Chert
Silicon dioxide (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and typically cryptocrystalline structure with variable colors.
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Physical properties
Hardness of 7 on the Mohs scale, waxy to vitreous luster, conchoidal fracture, and typically cryptocrystalline structure with variable colors.
Formation & geological history
Formed via the chemical precipitation of silica-rich solutions in marine environments or the replacement of limestone by silica over millions of years.
Uses & applications
Historically used for making stone tools and arrowheads due to its sharp conchoidal fracture; currently used for abrasive grinding and decorative landscaping.
Geological facts
Chert that is dark or black in color is commonly referred to as flint, which has been utilized by humans for fire-starting since prehistoric times.
Field identification & locations
Easily identified in the field by its high hardness, smooth waxy texture, and sharp curved fracture edges. Found worldwide in limestone and chalk 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
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