MLN 955 'Gove' Annual Report for the period 30 May 2016 to 29 May 2017

Abstract

During the anniversary period 30 May 2016 to 29 May 2017, Rio Tinto mined approximately 9.85 million dry product tonnes of bauxite at the Gove mining operation. Grade control drilling was undertaken on the Main Plateau and Rocky Bay Plateau. The 2016 drilling program was designed to infill 200m2 spaced holes to 50m2 spaced drilling to move resource estimation in those areas from indicated to measured. A total of 1,988 grade control vacuum drill holes for 8394m and 28,653 samples were completed. The 2016 Mineral Resource and Ore Reserve estimates were completed during the reporting period by RTA Bauxite Geology Team in Brisbane. Mineral resources are reported as at the 31 December 2016. The total 2016 Mineral Resource (exclusive of Reserve), including Inferred, Indicated and Measured classifications, is 44 Mdpt at 49.5% Al2O3 and 6.5% SiO2. The Mineral Resource was calculated with no block grade cut-off, but within a bauxite thickness envelope of at least 1m inside a plateau edge buffer of 25m. Although no cut-off has been applied to the model blocks, a mineralised bauxite envelope with a threshold of less than 16.0% SiO2 and greater than 40.0% Al2O3 was applied. The Ore Reserves estimated from the Mineral Resources, as at the 31s t of December 2016, are 147.1 Mdpt at 49.22% Al2O3 and 6.15% SiO2.