Where is Concretion with Limonite Core found?
Concretion (sedimentary rock) with Limonite (iron oxyhydroxide) core
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Open the appConcretion with Limonite Core occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Concretion with Limonite Core
United States
Widely distributed in sedimentary basins across the US, particularly in states with extensive sedimentary rock exposures such as Ohio, Kentucky, Illinois (e.g., Mazon Creek), and various Western states.
United Kingdom
Common in Jurassic and Cretaceous sedimentary formations, particularly in areas like Yorkshire and the Isle of Wight.
Canada
Found in sedimentary sequences across the country, including the Western Canadian Sedimentary Basin.
Australia
Present in various sedimentary deposits, often associated with iron-rich lateritic soils and weathered bedrock.
Collecting tips
- Look in Sedimentary Outcrops. Search for concretions in road cuts, riverbanks, coastal cliffs, and quarries where sedimentary rocks are exposed. They often weather out of softer host rock and accumulate at the base of slopes.
- Identify Host Rocks. Focus on areas with sandstones, siltstones, shales, and mudstones. Concretions are typically harder than the surrounding rock and may protrude from the outcrop.
- Check for Iron Staining. The presence of reddish-brown or yellowish-brown staining on the host rock can indicate the presence of iron oxides, which are often associated with limonite concretions.
- Break Open Suspect Specimens. Many concretions appear unremarkable from the outside. Breaking them open (with appropriate safety gear) can reveal the distinct limonite core and concentric layering.
Quick Check
- Color:
- Exterior: Variable (gray, tan, brown). Core: Yellowish-brown to reddish-brown.
- Luster:
- Exterior: Dull/Earthy. Core: Earthy/Dull.
- Streak:
- Yellowish-brown to brownish-yellow (for the limonite core).
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