Banded Iron Formation main content.

Banded Iron Formation

Part of Hall of Planet Earth.


A nearly 3-billion-year-old banded iron formation from Canada shows that the atmosphere and ocean once had no oxygen. Photosynthetic organisms were making oxygen, but it reacted with the iron dissolved in seawater to form iron oxide minerals on the ocean floor, creating banded iron formations.
The dark layers in this boulder are mainly composed of magneti