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Principal associates - Summary of principal associates (Detail) - shares | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Disclosure of associates [Line Items] |  |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 0 | 0 | 0
Boyne Smelters Limited [member] |  |  |
Disclosure of associates [Line Items] |  |  |
Group interest (%), Associate | 59.40% | 59.40% |
Boyne Smelters Limited [member] | Ordinary shares [Member] |  |  |
Disclosure of associates [Line Items] |  |  |
Company of operation, Associate | Boyne Smelters Limited |  |
Country of incorporation, Associate | Australia |  |
Principal activities, Associate | Aluminium smelting |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 153,679,560 |  |
Proportion of class held (%), Associate | 59.40% |  |
Group interest (%), Associate | 59.40% |  |
Mineracao Rio do Norte S.A. [member] |  |  |
Disclosure of associates [Line Items] |  |  |
Group interest (%), Associate | 12.00% |  |
Mineracao Rio do Norte S.A. [member] | Ordinary shares [Member] |  |  |
Disclosure of associates [Line Items] |  |  |
Principal activities, Associate | Bauxite mining |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 25,000,000,000 |  |
Proportion of class held (%), Associate | 12.50% |  |
Group interest (%), Associate | 12.00% |  |
Mineracao Rio do Norte S.A. [member] | Preferred Shares [member] |  |  |
Disclosure of associates [Line Items] |  |  |
Company of operation, Associate | Mineracao Rio do Norte S.A. |  |
Principal activities, Associate | Bauxite mining |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 47,000,000,000 |  |
Proportion of class held (%), Associate | 11.75% |  |
Mineracao Rio do Norte S.A. [member] | Common and preferred shares [member] |  |  |
Disclosure of associates [Line Items] |  |  |
Country of incorporation, Associate | Brazil |  |
Group interest (%), Associate | 12.00% |  |
Halco (Mining) Inc [member] | Common shares [member] |  |  |
Disclosure of associates [Line Items] |  |  |
Company of operation, Associate | Halco (Mining) Inc |  |
Country of incorporation, Associate | United States of America |  |
Rio Tinto Limited shares were held by Rio Tinto plc | 4,500 |  |
Proportion of class held (%), Associate | 45.00% |  |
Group interest (%), Associate | 45.00% |  |

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