Banded Iron Formation

A nearly 3-billion-year-old banded iron formation from Canada shows that the atmosphere and ocean once had no oxygen. 

Banded iron formation - Wikipedia

Photographs of Banded Iron Formations (BIFs); a view of a mine at

Hydrogeological constraints on the formation of Palaeoproterozoic

blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXs

Geology - A 2.1 billion-year-old banded iron formation

Banded iron formation in Barberton Mountain Land - Mountain

Banded Iron Formation stock image. Image of drilled - 176252629

banded iron formation

Banded iron formation - Wikipedia