MLN 955 Gove Annual Report for the period 30 May 2015 to 29 May 2016

Abstract

During the anniversary period 30 May 2015 to 29 May 2016, Rio Tinto mined approximately 8.2 million dry product tonnes of bauxite at the Gove mining operation. Grade control drilling was undertaken on the Main Plateau. The 2015 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 3,105 grade control vacuum drillholes for 8439.25m and 25,668 samples were completed. The 2015 Mineral Resource and Ore Reserve estimates were completed during the reporting period by RTA Bauxite Geology Team in Brisbane and utilised the same drillhole data \ resource model as used in the 2013 and 2014 estimation. Mineral resources are reported as at the 31st of December 2015. The total 2015 Mineral Resource (exclusive of Reserve), including Inferred, Indicated and Measured classifications, is 46 Mdpt at 49.3% Al2O3 and 6.2% 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 greater than 12.0% SiO2 and greater than 40.0% Al2O3 was applied. The Ore Reserves estimated from the Mineral Resources, as at the 31st of December 2015, are 145.4 Mdpt at 49.36% Al2O3 and 5.88% SiO2.