Cyanide leaching from a trial ROM leach pad resulted in recoveries of 75.12% for gold and 12.37% for silver after 81 days, said the firm. A recovery of approximately 60% for gold was achieved in the trial ROM heap within 30 days of leaching commencing.

The trial was conducted by Fenix Gold Limitada, the company's Chilean subsidiary, on a 426-tonne representative sample at a site located approximately 20 kilometres from the mine site at an altitude of 3,200 m.

A PFS in August 2019 had assumed crushing material to a size of 4 inches with recoveries of 75% for gold and 10% for silver. 

The testing targeted eliminating the need for the installation of a single-stage gyratory crusher.

Water used in the trial leaching was industrial water sourced from the Nueva Atacama water retreatment facility located in Copiapo. Rio2 has a water supply agreement with Nueva Atacama for industrial water for its 20,000 tpd mining project.

"The successful completion of the ROM heap leaching trial is an important milestone for Rio2 as it simplifies the mining and processing components of the Fenix Gold Mine by eliminating the need for installing a crusher and the subsequent double handling of mined material before its placed on the leach pad," said Alex Black, president & chief executive of Rio2.

"The resultant reduction of cyanide and lime consumption will also have a positive impact on the mine's operating costs. The results of this ROM test work were pending for the finalisation of the construction financing for the project."