Age: 2490–2450 million years, Paleoproterozoic
Location: Hamersley Range, Pilbara region
Formation: This banded iron-formation (BIF) was deposited from dissolved ferrous iron in the circulating waters of an early global ocean under a reducing atmosphere. The alternating bands show the marine environment see-sawing between oxygen-rich (dissolved iron precipitates) and oxygen-poor (silica precipitates), as microbial activity varied.
Significance: It is the distinctive, spectacular precursor of many of the globally significant Pilbara iron ore deposits and thus one of Australia’s most important rocks. Pilbara BIFs are the best exposed, least metamorphosed and least deformed BIFs on Earth and contain the world’s largest concentration of iron, amounting to billions of tonnes of minable ore.
Donated by: Fortescue Metals Group and the Government of Western Australia