sedimentary
Ironstone Nodule
Ferruginous Concretion
AI-generated identification · may be incorrectHardness 5-6 on Mohs scale; dark brown to reddish-brown color; dull to earthy luster; amorphous or microcrystalline crystal structure; irregular fracture; high specific gravity.
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Physical properties
Hardness 5-6 on Mohs scale; dark brown to reddish-brown color; dull to earthy luster; amorphous or microcrystalline crystal structure; irregular fracture; high specific gravity.
Formation & geological history
Formed through the chemical precipitation of iron oxides around a nucleus within sedimentary layers, typically during the diagenesis of sandstone or shale.
Uses & applications
Primarily collected as geological specimens or used locally as landscaping gravel and rustic decorative stone.
Geological facts
These nodules often weather out of softer surrounding strata due to their superior resistance to erosion, creating distinct resistant lumps.
Field identification & locations
Easily identified in the field by its heavy weight, dark rusty coloration, and spherical or irregular nodular form found embedded in sedimentary outcrops.
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Sandstone or Siltstone
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Shale
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