One of the world's major deposits of high-grade sedimentary manganese ore is on Groote Eylandt in the western section of the Gulf of Carpentaria in northern Australia.

Production and marketing of the ore commenced in 1966 after establishment of mining and treatment equipment together with ancillary facilities such as housing, roads, port facilities, water, and power supply. Subsequently, further detailed exploration, development, and metallurgical work resulted in the construction of a comprehensive ore-treatment and beneficiation plant and additional handling facilities.

Current production capacity is of the order of 1.25 million MT/yr of manganese ore, of which 80% is exported. An expansion program will provide for a production capacity of the order of 2 million MT/yr by the end of 1975, bringing the total capacity expenditure on the developments to approximately A$70 million.

The manganese ore is a tabular bed of approximately 30 km². It crops out adjacent to the western coastline of Groote Eylandt, and is covered by soft Tertiary and recent sediments.

Marine arenaceous Foraminifera of Early Cretaceous age have been identified from within the ore zone, and no apparent tectonic deformation of the zone has occurred.

The deposit appears to have been formed in a shallow-water environment, as it is associated with typical shallow-water sediments including unconsolidated clays and sands containing typical shallow-marine (inner sublittoral) faunal assemblages.