Exploration - the next steps

Identifying the minerals

We identify mineralisation within our selected area, after we have secured a licence to explore. We may conduct geophysical and geological surveys or take rock samples and stream sediments for geochemical analysis. As this stage of the process, minor clearing of vegetation is the only thing required, there is little scope to cause environmental damage. We talk to communities at this stage to secure temporary access to land. So there may be opportunities for short term local employment and we may use local services and supplies.

Testing

Once we have identified prospects with potential, we conduct "preliminary sub-surface evaluation". This may involve constructing a limited access track, a camp, trenches and drill holes. Our environmental management plan ensures that all drilling activities adhere to best practice standards. Perhaps one in 30 of the prospects at this stage will prove to be of interest and the remainder will be abandoned without further work.

Resource "delineation"

Next we establish the size, metallurgy and grade of the deposit. This involves additional drilling to estimate the extent of ore grade mineralisation. Work may also involve extensive clearing for access tracks, larger camp construction and drill sites. We may conduct baseline environmental and community studies at this stage. The resource delineation phase will provide opportunities for local employment and service provision. Out of the many prospects we investigate, perhaps one in five of the ones that receive delineation drilling will prove to have development potential for Rio Tinto.

Resource evaluation

To evaluate a resource involves more detailed investigation of the deposit under the direction of a Rio Tinto business unit. This work involves infill drilling to accurately measure the size and grade of the deposit, metallurgical studies to assess metal recoveries from the ore and a preliminary assessment of project economics. At this stage the main objective is to look at all available options on how to mine and beneficiate (process) a deposit - with the aim to select the best combination by the end of the study. A potentially attractive project for Rio Tinto will be identified from perhaps one in two of the deposits that proceed through the resource evaluation stage.

Feasibility

Evaluating the feasibility of recovering the ore is the final stage of the exploration process. It involves detailed geological, metallurgical, engineering and financial studies that will allow Rio Tinto to refine the best methods on how to mine and process the particular deposit. Most deposits that proceed through feasibility will be mined.