Where is Goethite Concretion found?
FeO(OH)
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Open the appGoethite Concretion 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 Goethite Concretion
United States
Widely distributed. Notable occurrences include the Lake Superior region (associated with iron formations), various sedimentary basins (e.g., Cretaceous deposits in the Western Interior Seaway), and bog iron deposits in eastern states.
Germany
Type locality for goethite is the Hollertszug Mine, Herdorf, Siegerland. Concretions are found in various iron ore districts.
United Kingdom
Common in Jurassic ironstones (e.g., Cleveland Ironstone Formation) and as bog iron deposits.
Australia
Abundant in lateritic soils and iron ore deposits, particularly in Western Australia.
Brazil
Major component of vast iron ore deposits, especially in Minas Gerais, where it forms significant portions of lateritic and banded iron formations.
Collecting tips
- Look in Sedimentary Environments. Search in areas with exposed sedimentary rocks, particularly sandstones, shales, and limestones, where iron-rich groundwater has circulated. Riverbeds, stream banks, and coastal exposures can be productive.
- Identify Iron Staining. Goethite concretions are often associated with reddish-brown or yellowish-brown iron staining in the surrounding rock or soil. This indicates the presence of iron oxides/hydroxides.
- Check for Spherical or Irregular Shapes. Concretions typically stand out from the host rock due to their distinct, often rounded or irregular shapes. They may weather out of softer sediments.
- Test Streak Color. A characteristic yellowish-brown to brownish-yellow streak is a key diagnostic feature for goethite and goethite-rich concretions, distinguishing them from hematite (red streak).
- Examine Boggy or Swampy Areas. In regions with historical or active bog iron formation, look for dark, heavy, rusty-looking masses in shallow water or peat deposits.
Quick Check
- Color:
- Dark brown to yellowish-brown
- Luster:
- Dull, earthy, submetallic
- Streak:
- Yellowish-brown to brownish-yellow
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