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 tons of manganese ore per annum, of which 80% is exported. A new expansion program will provide for a production capacity of the order of 2 million tons per annum by the end of 1975, and bring the total capital expenditure on the developments to approximately $65 million.

The manganese ore is a tabular bed approximately of 13 sq mi. It crops out adjacent to the western coastline of Groote Eylandt, and is covered by soft Tertiary and recent sediments.

The ore exhibits varied physical characteristics ranging from fine loose powdery material to unconsolidated oolites and pisolites and to massive laterite and cemented boulders of pisolites. It ranges in thickness from 0.5 to over 15 m, and is present over a 45-m stratigraphic interval of 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 has the appearance of having been formed under shallow-water conditions, being associated with typical shallow-water sediments including unconsolidated clays and sands containing typical shallow-marine (inner sublittoral) faunal assemblages.

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