Rio Tinto's 2017 annual report includes significant changes in estimates of Ore Reserves and Mineral Resources at Rio Tinto's Argyle Diamond mine in the East Kimberley, Western Australia, the company announced in a press release accompanying their annual report. The substance of the announcement is not new, but confirms their June 2017 notice that the miner had lowered by 66% its estimate of the mineral resources available at its Argyle diamond mine in Australia, specifying at the time that the estimate reflected solely the current mine plan, whereas the previous estimate included resources calculated with an extension of the mine taken into account.
And while they had previously stated the extension of the mine was under review, they now say, "Following further reviews of resource development potential, and with the reduction in the Argyle Ore Reserve and the limited remaining mine life, the other mineralised deposits at Argyle do not demonstrate economic prospects and are not scheduled for production. As such, Argyle Mineral Resources, exclusive of Ore Reserves, decreased from 15Mt to 0Mt." The comment in their annual report states that during 2017, estimated Argyle Ore Reserves decreased by 13Mt from 29Mt to 16Mt. This decrease includes depletion of almost 5Mt due to production activities in 2017. The balance of the reduction results from a more conservative view on future production performance, grade and economic shut-off criteria. The remaining reserves underpin the operation until 2020, with opportunities to increase reserve estimates and extend the operational life subject to technical and financial performance.