sedimentary
Ironstone Concretion
Ferruginous Concretion / Limonite-Goethite Aggregate
AI-generated identification · may be incorrectHardness of 4-5.5 on the Mohs scale, rusty brown to dark reddish-black color, dull to submetallic luster, amorphous to microcrystalline structure, and uneven fracture.
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Physical properties
Hardness of 4-5.5 on the Mohs scale, rusty brown to dark reddish-black color, dull to submetallic luster, amorphous to microcrystalline structure, and uneven fracture.
Formation & geological history
Formed by the precipitation of iron oxides cementing surrounding sedimentary particles in groundwater environments, often occurring in sandstone or shale formations.
Uses & applications
Primarily collected as a geological curiosity, used in landscaping, or occasionally as a low-grade iron ore historically.
Geological facts
These nodules often form around a nucleus like a fossil or mineral grain and can weather into peculiar, hollow shapes resembling meteorites or artifacts.
Field identification & locations
Easily identified in the field by its distinct reddish-brown rust color, high density, and rounded, sometimes fracture-patterned exterior found embedded in sedimentary strata.
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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