The Nammuldi mine is located in the Hamersley Group which forms the middle layer of Mount Bruce Group in the Marra Mamba Iron Formation.

The Marra Mamba Iron Formation is the lowermost unit of the Proterozoic Hamersley Group in the northwestern part of Western Australia.

The Marra Mamba Iron Formation varies considerably in thickness, as based on sections measured in the field; however, not enough drill hole data are available to provide a quantitative assessment of its thickness variation throughout the Hamersley Range. Trendall and Blockley repoft a thickness range of 183 to 229 m based on sections mearPresent address: Department of Geology, Georgia State Univcrsity, Atlanta, Georgia

Others report thicknesses that range from a minimum of 15 m to 183 m (Macleod, 1966) for sections in different parts of the Hamersley Range. The Marra Mamba lron Formation is underlain by the Jeerinah Formation which is the uppermost member of the Fortescue Group. This group may be as much as 3660 to 4270 m thick and consists of shales and cherts in the upper part.

All of Hamersley Iron's mines are conventional open pits. Ore is loaded into haul trucks by shovels, hydraulic excavators or front-end-loaders, and transported to the primary crusher. It is then processed in a crushing and screening plant to produce fine ore and lump ore.

Transportation of ore to Tom Price mine for processing at a central processing facility via the existing overland conveyor. The existing haul road from Tom Price mine to S10 BRK, which runs parallel to the S10 overland conveyor, is the main access for heavy vehicles (including haulage of ore and transport of explosives).

Processed ore is transported from Tom Price mine via the existing Rio Tinto railway network to existing Rio Tinto port facilities located at Cape Lambert and Dampier. At Mount Tom Price, a high-grade plant produces lump product, fines and oversize. The low-grade ore feeds the concentrator, undergoes HMS and wet high intensity magnetic separation.