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:: Newmont’s Verde Bioleach Project Explores New Frontiers
Minera Yanacocha in Peru is Latin America’s largest gold mine, yielding more than 34 million ounces of gold since the mine began producing in 1993. However, with a projected remaining mine life of approximately five years, and a progressive decline in the gold grade in the mine’s ore bodies, Yanacocha is nearing the final stages of its lifecycle. Or, at least, that was the assumption.
Newmont's Verde Bioleach Demonstration Facility produced its first copper cathode in September 2013After intensive laboratory research, a new way to extend the life of this prolific asset is showing promise. Our talented team is developing a way to safely and economically recover copper from a sulfide ore body dominant with the mineral enargite - a first in the mining industry.
For more than a decade, a vast deposit of enargite dominant mineralization located beneath Yanacocha’s oxide (gold) ore body was avoided due to its complexity and cost to process. “Because the enargite dominant mineralization exists at significant depth beneath the earth’s surface and more difficult to process, it didn't rank high enough among our other projects to warrant further exploration," says Mike Skurski, Senior Director of Projects at Newmont.
Ten years later, as the Yanacocha mine entered into the latter part of its mine life, Newmont’s mineralogists decided to re-examine the enargite ore. “For several years we examined and studied samples from the sulfide deposit, testing one variable at a time in our lab," says Skurski.
What his metallurgical colleagues learned was that the sulfide ore at Yanacocha contains microorganisms that make it conducive to copper production. To prove technical and commercial viability of copper production at Yanacocha through a process known as bioleaching, Newmont launched the Verde Bioleach Demonstration Facility (VBDF) in 2010. “No one in the industry had cracked the code to producing copper economically and safely from enargite," says Skurski.
However, Newmont had some success experimenting with bioleaching, a process that uses the chemicals produced by microorganisms already present in the ore to oxidize, recover, and refine the mineral into a pure metal. Specifically, we discovered which chemical properties must be present in order to accelerate oxidation of the copper minerals in the ore. “This type of rock doesn’t leach quickly," explains John Uhrie, Manager of Process Metallurgy at Newmont. “And because of the amount of time and money it takes to process it, industry perception has always been that it is not economically viable to pursue."
Newmont’s discovery challenged that assumption and provided enough evidence to support moving the research from our lab in Denver to Yanacocha so more testing could take place under actual field conditions. “We couldn't have developed a business case for this type of processing based on lab research alone," explains Skurski. “We knew we’d have to find out if it could be equally successful at Yanacocha’s elevation, its climate and under a variety of other conditions. In 2012, we began construction on a demonstration-sized facility at our Yanacocha operations so we could test our bioleaching process on site."
In September 2013, just one month after completion of the demonstration facility, the VBDF team harvested its first copper cathode - a pure, solid plate of copper. “The copper cathode is just one step along the way to understanding if we have an economically viable project," says Uhrie.
Over the next two years, Newmont plans to develop the science behind this process. If field-testing continues to produce positive results, the VBDF team will evaluate building a full-scale commercial facility. Potentially, that facility could extend Yanacocha’s mine life by 20 years and yield a total of more than two to three billion pounds of copper over the life of the operation. “Verde is an example of how, after years of focusing primarily on gold, we’re diversifying our assets by developing more copper projects," Skurski says. “At Yanacocha, where our oxide gold resources will eventually run out, we have the potential to evolve a successful gold mine into a successful copper mine. Verde aligns perfectly with our strategic vision of targeting gold and copper investments that can increase the value and life of a mine."
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