sedimentary
Chert
Microcrystalline quartz (SiO2)
AI-generated identification · may be incorrectHardness of 7 on the Mohs scale, earthy to waxy luster, concoidal fracture, and variable colors including tan, brown, white, and grey.
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Physical properties
Hardness of 7 on the Mohs scale, earthy to waxy luster, concoidal fracture, and variable colors including tan, brown, white, and grey.
Formation & geological history
Formed through the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of marine organisms over millions of years.
Uses & applications
Historically used for making stone tools like arrowheads and blades due to its sharp concoidal fracture, and occasionally utilized in landscaping or decorative masonry.
Geological facts
Chert is extremely durable and resistant to weathering, often outlasting the surrounding limestone matrix in which it is frequently found as nodules.
Field identification & locations
Identify in the field by its distinct waxy luster, high hardness that scratches glass, and sharp, curved fracture edges. Commonly found in limestone and chalk deposits worldwide.
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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