sedimentary
Limestone Concretion
Calcium Carbonate Concretion (CaCO3)
AI-generated identification · may be incorrectHardness of 3 on the Mohs scale, typically buff, tan, or brown in color with an earthy to dull luster, and massive or cryptocrystalline structure.
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Physical properties
Hardness of 3 on the Mohs scale, typically buff, tan, or brown in color with an earthy to dull luster, and massive or cryptocrystalline structure.
Formation & geological history
Formed by the precipitation of mineral cement within the pores of sedimentary rocks, typically growing around a nucleus in shallow marine environments.
Uses & applications
Used primarily as educational geological specimens, aggregate in construction, or agricultural lime when processed.
Geological facts
These rounded masses often weather out of softer surrounding shale or limestone layers due to differential erosion.
Field identification & locations
Identify in the field by their spherical or irregular nodular shape and a positive fizz reaction when tested with dilute hydrochloric acid.
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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