Changes to Mineral Resources and Ore Reserves

Changes in Rio Tinto's Pilbara iron ore Mineral Resources and Ore Reserves between the end of 2019 and the end of 2020 are shown below in Table A and Table B respectively.

Table B - Aggregate changes to Rio Tinto's Pilbara iron ore Mineral Resource estimates

between 31 Dec 2019 and 31 Dec 2020 (100% basis)

Table C - Aggregate changes to Rio Tinto's Pilbara iron ore Ore Reserve estimates

between 31 Dec 2019 and 31 Dec 2020 (100% basis)

Iron ore Ore Reserves are reported as dry product tonnes.

Rio Tinto Aluminium Pacific Operations Ore Reserve and Mineral Resource Estimates

The RTA Pacific Operations Ore Reserve estimate has decreased by 305 Mt, from 1,530 Mt to 1,224 Mt.  The reduction in Ore Reserve estimate is associated with a routine review of price assumptions over the life of the mine.  There has been no material change to the economic cut-off methodology or process.  The application of the updated pricing assumptions has removed lower quality material from the Ore Reserve estimate.  There has been no material change to the other reserve modifying factors, including: governmental, tenure, environmental, cultural heritage, social, community or operational.

RTA Pacific Operations Mineral Resources exclusive of Ore Reserves has increased by 128 Mt, from 1,949 Mt to 2,077 Mt (This includes 1,330 Mt of Inferred Resource at North of Weipa, which remains unchanged from 2019). The increase was mainly due to changes in the forecast pricing assumptions used in the reserving process. Those blocks removed from the 2020 Ore Reserve that are physically located above or below the remaining economic blocks have also been removed from the Mineral Resource.

Mineral Resources at Kennecott Copper

There are significant additional Measured, Indicated and Inferred Mineral Resources at the Kennecott Copper operation.  These Mineral Resources are contained within the Bingham Canyon copper, gold, and molybdenum porphyry deposit and would be mined by a northernly expansion of the open pit located 41 km southwest of Salt Lake City, Utah.

Total Mineral Resource increase reported at an economic margin is 243 Mt at 0.55% copper equivalent (CuEq), an increase of 577%. The additional Mineral Resources potentially add about four years of mine life to the Bingham Canyon open pit if converted to Ore Reserves through additional study.  As announced in 2019, work is currently underway to extend production at Kennecott to 2032.

A full tabulation of the changes in Mineral Resource from 2019 to 2020 is provided in Table D, including the additions of Measured, Indicated and Inferred Mineral Resource based on Order of Magnitude (OoM) study open pit phase designs and optimised economic cut-off grade constrained within the resource shell.

Table D: Mineral Resource changes for Bingham Canyon Open Pit

The Mineral Resource additions at the Kennecott Copper operation for 2020 are constrained within OoM open pit expansion phase designs and have been tabulated based on production schedules using optimised varying economic margin cut-off grades which averaged approximately equal to a 0.25 CuEq%.  Depletions are due to 2020 mining of Inferred Resource within the Bingham Canyon Ore Reserve pit. 

Copper equivalent is determined using Rio Tinto forward-looking pricing and metallurgical recovery assumptions which are summarised in the Important notices below.

Important notices

Iron Ore Mineral Resource and Ore Reserve estimates

The Iron Ore Mineral Resource and Ore Reserve estimates referred to in this release were set out in the release to the ASX dated 17 February 2021 "Changes to Iron Ore Mineral Resources and Ore Reserves" (RTIO release).  The Competent Person responsible for the information in the RTIO release that relates to Mineral Resources is Mr Bruce Sommerville, who is a Fellow of the Australasian Institute of Mining and Metallurgy (FAusIMM). The Competent Person responsible for the information in the RTIO release that relates to Ore Reserves is Mr Rishi Verma who is a Member of the Australasian Institute of Mining and Metallurgy (MAusIMM).   

RTA Mineral Resource and Ore Reserve estimates

The Mineral Resource and Ore Reserve estimates for RTA referred to in this release were set out in the release to the ASX dated 17 February 2021 "Changes to Rio Tinto Aluminium Pacific Operations Ore Reserve and Mineral Resource Estimates" (RTA release).  The Competent Person responsible for the information in the RTA release that relates to Mineral Resources is Mr Angus C. McIntyre, who is a Member of the Australasian Institute of Mining and Metallurgy (MAusIMM).  The Competent Person responsible for the information in the RTA release that relates to Ore Reserves is Mr William Saba who is a Member of the Australasian Institute of Mining and Metallurgy (MAusIMM). 

Copper Mineral Resource estimates

The Mineral Resource estimates for Kennecott Copper referred to in this release were set out in the release to the ASX dated 17 February 2021 "Increase in Mineral Resource at Kennecott Copper operation following mine life extension studies" (RTK release).  The Competent Persons responsible for the information in the RTK release that relates to Mineral Resources are Kim Schroeder and Pancho Rodriguez, who are Members of the Australasian Institute of Mining and Metallurgy (MAusIMM).

Copper equivalents referred to in this release have been calculated using the formula CuEq% = Cu% + (((Au g/t * Au price per gram * Au_recovery) + (Mo% * Mo price per tonne * Mo_recovery) + (Ag g/t * Ag price per gram * Ag_recovery)) / (Cu price per tonne * Cu_recovery). Metal prices used are provided by Rio Tinto Economics and are generated based on industry capacity analysis, global commodity consumption and economic growth trends. A single long term price point is used in the definition of ore and waste and in the financial evaluations underpinning the resources statement. The detail of this process and of the price points selected are commercially sensitive and are not disclosed. Operating costs are informed by current operations. Average grades for the individual metals included in the metal equivalent calculation are shown in the Mineral Resource tabulations. Average metallurgical recoveries for the resource additions used to calculate CuEq% are:

It is the company's opinion that all the elements included in the metal equivalent calculation have a reasonable potential to be recovered by Rio Tinto Kennecott's milling, smelting and refining facilities and sold.

No new information

Rio Tinto confirms that it is not aware of any new information or data that materially affects the information included in the RTIO release, the RTK release or the RTA release (together, the ASX releases), that all material assumptions and technical parameters underpinning the estimates in the ASX releases continue to apply and have not materially changed, and that the form and context in which the Competent Persons' findings are presented have not been materially modified.