It now has more time to acquire land or to reach legal agreements with landowners to build a processing plant and associated infrastructure at the mine site.
The drop to 64.057 million tonnes came as several major operations remained fully or partially shut down in the second quarter following a deadly dam burst at the Corrego do Feijão mine.
Proven and probable copper mineral reserves increased by 21% since the end of 2018 to 11.8 billion pounds, while gold mineral reserves gained 12% to reach 7.4 million ounces.