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Banded Iron Formation

The layers of red chert and gray, iron-rich hematite record seasonal changes in ocean waters. The iron oxide precipitated when warm, oxygen-bearing water from the surface mixed with cold, iron-rich water beneath it.

Group: Sedimentary
Catalog Number: 75535
Time Period: 2.1-1.8 billion years old
Collected by G. A. Merrill
Locality: Ishpeming, Marquette County , Michigan


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Smithsonian National Museum of Natural History Department of Mineral Sciences website Credits