The combined open-pit and underground mine located near Khanbogd in Mongolia's South Gobi region met more than 30 criteria needed for responsible environmental, social and governance operating practices per an independent review.

The Copper Mark distinction was first developed by the International Copper Association, formed by input from stakeholders such as customers, producers and NGOs.

"At Turquoise Hill, we are fully committed to responsible production and transparency at Oyu Tolgoi," Turquoise Hill CEO Ulf Quellmann said.

Oyu Tolgoi has been developing a health, safety and environmental management system since 2010 to be in compliance with IOS 14001 Environmental and OHSAS 18001 Occupational Health and Safety management standards. It was audited independently in 2013 and earned certification in those standards, the miner said.

Turquoise Hill's ownership in Oyu Tolgoi is held through a 66% interest in Oyu Tolgoi LLC; Mongolian state-owned entity Erdenes Oyu Tolgoi holds the remaining 34% interest. Rio Tinto owns 50.8% of Turquoise Hill Resources and manages the operation on behalf of the owners.