Hamersley Basin, Western Australia

The Hamersley Basin comprises Lower Proterozoic sediments and volcanic rocks. Within the Hamersley Group three major iron formations are separated by shales, dolomite and acid volcanics. Although the iron formations have been folded, they are essentially unmetamorphosed. Extensive supergene enrichment has produced high grade haematite ores, as well as major secondary limonite-rich ores. The main ore type is very finely interbanded iron oxide and chert and is uniform over vast areas.

Major Minerals:

Haematite, limonite

Minor Minerals:

Magnetite, stilpnomelane, minnesotaite, siderite, dolomite/ankerite, pyrite


Iron oxides/hydroxides occur as fine laminae interbanded with chert. Fine banding of magnetite, haematite and limonite occur within the iron-rich laminae. Haematite forms coarse tabular crystals between the fine-grained laminae and is associated with limonite. Magnetite is altered to haematite (martitization) and limonite


Ayres, 1972; Morris, 1980; 1985