Rocksday

Banded Iron Formation

Ancient rock of alternating red chert and silvery iron oxide bands, mostly 1.8–2.5 billion years old.

Banded Iron Formation specimen
Photo: James St. John, CC BY 2.0, via Wikimedia Commons

How to identify banded iron formation

  • Striking red and steel-gray stripes.
  • Heavy.
  • Silver bands leave a red-brown streak (hematite).

Often confused with

Where it's found

  • Hamersley Range, Western Australia
  • Mesabi Range, Minnesota
  • Carajás, Brazil

Uses

The world's main iron ore source.

Rock tumbling

Great for tumbling.

Did you know?

These rocks record how early microbes first filled the oceans and air with oxygen.

Think you could spot it from a blurry close-up?

Play today's Rocksday