Banded iron formation (BIF)
A sedimentary rock of alternating bands rich in iron oxide and silica, deposited mainly between 3.8 and 1.8 billion years ago, when oxygen was appearing in the ocean. It is the world’s main source of iron ore.
Composition
Minerals: hematite, magnetite, chert (silica), siderite; ore enriched to over 60% iron.
Sources
In the atlas
- Carajás Brazil
- Isua (BIF) Greenland
- Gongchangling China
- Cauê Formation (Quadrilátero Ferrífero) Brazil
- Zankan China