Researchers have been able to show for the first time how microorganisms contributed to the formation of the world's biggest iron ore deposits. The biggest known deposits -- in South Africa and Australia -- are geological formations billions of years old. They are mainly composed of iron oxides -- minerals we know from the rusting process. These iron ores not only make up most of the world demand for iron -- the formations also help us to better understand the evolution of the atmosphere and climate, and provide important information on the activity of microorganisms in the early history of life on Earth.

Source: Iron in primeval seas rusted by bacteria