Posted by Daniel Gleeson on March 1, 2021
Bluestone Resources has presented a new surface mining plan for its Cerro Blanco project in southeast Guatemala, which effectively doubles production and triples potential returns to investors from the gold-silver asset.
Cerro Blanco’s preliminary economic assessment, which comes just under 11 months after entering into an agreement with G Mining Services covering basic engineering and overall project optimization efforts, describes a project capable of producing 231,000 ounces of gold at an all-inclusive price. maintenance cost of $ 642 / oz Au over the 11 year life of the mine. This is based on a 15,000 tpd operation with an initial investment bill of $ 548 million.
Using a benchmark gold price of $ 1,550 / oz and a silver price of $ 20 / oz, an after-tax net present value (5% discount) of $ 907 million was calculated .
The numbers are very different from what the company reported in a previous feasibility study on Cerro Blanco, carried out by a consortium of independent consultants led by JDS Energy & Mining. This showed an average production of 113,000 oz / yr of gold at an all-inclusive sustaining cost of $ 579 / oz and a capital cost of $ 196 million (including contingencies).
Using a baseline scenario of $ 1,250 / oz gold and $ 18 / oz silver, this underground project was estimated to generate an after-tax net present value (5% discount) of $ 241 million. .
Bluestone said on the PEA publication: “The recent completion of advanced engineering and optimization work has dramatically improved understanding of the project and presented an opportunity to capitalize on its high-grade mineralization near surface through a open-air development scenario. This is a major change in Bluestone’s corporate strategy that will fully maximize the value of the Cerro Blanco gold project for all stakeholders.
David Cass, Vice President of Exploration, added: “The pivot to surface mining is the culmination of our increased understanding of the geology and grade distribution that will allow the full potential of mine to be realized. the low-grade Cerro Blanco mineralization. The inverted wedge shape of the deposit with its upper half forming the Cerro Blanco hill lends itself to surface mining with a low stripping ratio.
The Project currently contains 3 Moz of gold in the Measured and Indicated Resource category and 250,000 oz of gold in the Inferred Mineral Resource category.
The surface mining scenario envisions an owner operated mining fleet using 65 t trucks combined with 7 m3 hydraulic excavators supported by 8.2 m3 wheel loaders. The crusher feed will be trucked to a primary crusher located east of the main pit. Waste totaling 123.5 Mt will be placed in a waste storage facility.
In terms of processing, the PEA plans to process 5.04 Mt / a of mineralized material at an average feed grade of 1.6 g / t Au and 7.26 g / t Ag via a leach treatment plant at conventional cyanide to produce gold. The schematic diagram is very similar to the previous underground mine option and includes primary crushing, single train SAG mill and ball mill to produce 80% target crush size increasing to 53 microns, atmospheric preoxidation , a 48-hour cyanide leaching, carbon in the adsorption circuit of the pulp carousel, Zadra elution circuit, gold room and filtered tailings. Based on the metallurgical tests of the PEA, the expected recoveries are 91% for gold and 85% for silver.
The filtered tailings will be configured in a dry cell facility and eliminate the need to build and operate a traditional tailings facility, according to the company.
“The adoption of this technology (dry stacking) places the Cerro Blanco project at the forefront of responsible mining practices adopted for the future of sustainable mining on a global scale,” he said. added.