sedimentary
Concretion
Sedimentary Concretion
AI-generated identification · may be incorrectVariable hardness depending on composition; earthy colors (brown, tan, gray); dull luster; irregular, nodular, or bulbous shape; no distinct cleavage.
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Physical properties
Variable hardness depending on composition; earthy colors (brown, tan, gray); dull luster; irregular, nodular, or bulbous shape; no distinct cleavage.
Formation & geological history
Formed in sedimentary rock by the localized precipitation of mineral matter around a nucleus, often during early diagenesis.
Uses & applications
Primarily collected as curiosities by rockhounds; no major industrial value.
Geological facts
Concretions can sometimes contain well-preserved fossils at their centers, acting as protective nodules. They are often mistaken for meteorites or dinosaur eggs due to their unusual shapes.
Field identification & locations
Identified by their distinctive rounded, nodular, or botryoidal shapes that stand out from the surrounding host rock. Commonly found in shale, sandstone, or mudstone deposits.
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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