Rio2 Ltd has announced positive results obtained from the ROM heap leaching trial for its Fenix Gold Project in Chile. The ROM heap leaching trial was conducted by personnel of Fenix Gold Ltda, the Chilean subsidiary of Rio2 Ltd, and overseen by HLC Ingeniería y Construcción, Rio2’s independent metallurgical consultants who were awarded the process plant/site infrastructure construction contract for the Fenix gold mine last year.
Material for the trial heap was drilled and blasted from areas of the Fenix North, Fenix Central and Fenix South deposits and composited to make a 426 t representative sample. The trial was conducted at Rio2’s infrastructure site located approximately 20 km from the Fenix Gold mine site at an altitude of 3,200 m.
The objective of the metallurgical test work was to determine whether ROM processing could be implemented at the Fenix gold mine. The test work targeted simplifying operations and eliminating the need for the installation of a single stage gyratory crusher as outlined in the PFS with an effective date of August 15, 2019. Apart from determining metal recoveries, the metallurgical test work has broadened the company’s understanding of mineral comportment, leach pad irrigation rates, cyanide percolation rates, leach kinetics and dosage and consumption of cyanide and reagents.
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 t/d mining project.
The average grade of the composite material in the trial pad was 0.46 g/t gold, 0.43 g/t silver and 0.02% copper. Cyanide leaching of the material in the trial ROM leach pad took place over 81 days resulting in recoveries of 75.12% for gold and 12.37% for silver. These results compare favorably with those from the August 2019 PFS which assumed crushing material to a size of 4 in with recoveries of 75% for gold and 10% for silver. It is important to highlight that a recovery of approximately 60% for gold was achieved in the trial ROM heap within 30 days of leaching commencing.
Cyanide consumption averaged 0.18 kg/t and lime consumption averaged 2.95 kg/t. The PFS assumed cyanide consumption of 0.4 kg/t and lime consumption of 4 kg/t. The percolation rate in the trial heap was 2.4 m/day. Copper dissolved in the pregnant solution averaged 12 ppm which indicates that the low copper content will not inhibit the adsorption process. The granulometric analysis for the composited ROM material determined that the size fraction for 75% of the material was less than 3 in, and 94% passing 5 in which makes management feel that it will be possible to improve gold recoveries further by optimising the blasting design for mineralized material during mining.
Alex Black, President & CEO of Rio2, stated: “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. 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.”
