The association developed the accolade in 2017 in pursuit of responsible sourcing strategy options for copper, modelling it on the United Nations Sustainable Development Goals.

After extensive stakeholder consultation, pilot assessment with 25 member companies, and standards refinement, the Copper Mark was launched in March. The Copper Mark is now an independent entity with a multi-stakeholder council.

"We are proud to lead the copper industry in being awarded the Copper Mark, demonstrating our commitment to responsible production and transparency," said Rio's copper and diamonds CEO Amaud Soirat.

"The Copper Mark allows our customers to purchase copper from operations that have been independently assessed as meeting the highest environmental, social and governance standards, responding to the growing expectations of consumers around the world for sustainable supply chains."

International Copper Association president, Tony Lea said: "The Copper Mark is an important milestone for the global copper industry and reflects stakeholders' needs for greater transparency. We hope more producers will follow Rio Tinto's lead and apply for the Copper Mark."

Among the assessment criteria are categories for the environment, community, business and human rights, labour and working conditions and governance.

Rio said last week the Kennecott mine that started operations in 1903 had experienced delays to a restart of the smelter due to unexpected issues that appeared following planned maintenance. The company said it was working to limit disruptions to customers and expected to have the smelter fully operational in two months.

As a result, Rio Tinto group production guidance for refined copper in 2020 was lowered to 135,000-175,000t from 165,000-205,000t previously.