Curis Resources acquired the Florence Cooper project and its existing infrastructure in 2009 | All images courtesy of Curis Resources
Those familiar with the area have known the potential of the deposit that Curis Resources is developing in central Arizona for some time. Now the Canadian company aims to make good on that promise by developing an in-situ copper recovery operation that CEO Michael McPhie proudly calls “the best in-situ extraction opportunity globally.”
The Florence Copper project is situated on a copper belt that crosses Arizona and hosts several mines. Many of these employ or have employed in-situ copper recovery (ISCR) as an auxiliary operation to their open pits, recovering additional copper from their pit walls – most notably BHP Billiton’s Miami East and San Manuel mines, and Freeport-McMoRan’s Cyprus Tohono. “The difference with these other projects,” says McPhie, “is that Florence is a stand-alone in-situ leaching (ISL) project, as opposed to a combination of conventional mining and ISL extraction.”
“Florence is an exciting opportunity because this deposit is a lot more fractured,” says Dan Johnson, vice-president, environment and technical services. “Mother nature’s been very kind to us in that there’s intense geological faulting in this area, and intense geological fracturing of these faults.” The copper occurs as fine-grained mineralization on the fractures of the rock, and the high amount of fracturing makes it ideal for an ISCR operation.
The first company to show interest in the site was Conoco in the 1970s, who looked at developing an open-pit operation. Company officials found there was too much water in the ground, however. Says Johnson: “With the oxide bedrock being so fractured, and being right next to a major river system in Arizona, there’s a lot of water coming in to the deposit – 30,000 gallons [113,000 litres] per minute or more.”
At the time, Magma Copper was operating a large ISCR project at its nearby San Manuel mine, which produced 15 million to 20 million pounds (6,800 tonnes to 9,000 tonnes) of copper from in-situ operations annually before shutting down in the late 1990s. “San Manuel was an open pit operation,” says McPhie, “but the operators had also targeted a lot of the buried oxide material with well-to-well leaching like we’re proposing to do. They identified the advantage that the operating costs of the ISL project were a fraction of the open-pit costs. At the time they could get copper out of the ground for 40 cents/pound to 45 cents/pound [$.90/kg to $1.00/kg], and the costs for conventional mining were double or triple that.”
Magma acquired the Florence property in 1992; it later completed a feasibility study and began detailed engineering on the development of an in-situ copper recovery/solvent extraction electrowinning (SX/EW) copper mining operation at the site. When BHP took over Magma in 1996, the company continued developing the site, obtaining full commercial operating permits and initiating an ISCR pilot test between 1997 and 1998 with a well field of 24 wells.
But then the market dipped, and copper fell to $1.30/kg. BHP pulled the plug on the operation. “It was really a tough time in the marketplace,” says McPhie, “particularly for base metals, when copper was a fraction of what it is today.”
Curis formed in 2008, intent on acquiring the Florence property, which it did in December 2009. Curis is now a publicly traded company, with close ties to Hunter-Dickinson (HDI). HDI initially sponsored Curis when it was a private company and remains the largest shareholder at 24 per cent. “We are pretty tightly linked,” says McPhie. “We are an independent company, but we do draw on a lot of the HDI resources and professionals – engineering, environmental, accounting, marketing and investor relations.”
Now that Curis has taken over the Florence property, it is reaping the benefits of BHP’s earlier development. There is a lot of infrastructure already in place including roads, water and power systems, a water pond, a well field, an office building and laboratory, and a garage and mechanics facility.
“BHP invested upwards of $60 million looking at this project over a four- or five-year period,” says McPhie. “So, our starting point on this is a tremendous intellectual catalogue of information and tests. What we acquired here is a project with a pre-feasibility study done on it, with permits in place, and with a pilot test already run on it, showing that it’s effective.”
The permits were kept up, and Curis is now amending and updating these, an 18-month process that they expect will be completed by mid-2012, along with a feasibility study. As well, because BHP’s leaching of the ore only ran for 100 days, Curis is running its own pilot test to conclude data gathering required by regulatory agencies. It will consist of another 24 wells, this time targeting a deeper section of the deposit. “We’re going to get tremendous information from this new test because we’re testing the most challenging part of our ore body,” says Johnson.
According to Curis’ studies, the Florence property contains 429 million tonnes measured and indicated copper oxide resource, grading 0.331 per cent copper and containing 1.28 million tonnes of copper. Johnson says, “The deposit begins at about 400 feet [120 metres] and extends down to about 600 feet [180 metres] in the eastern portion and 1,200 feet [365 metres] in the western portion. But the average thickness is about 500 feet [150 metres].” Full commercial production of this copper is expected by mid-2014.
Infrastructure already in place includes roads, water and power systems, a water pond, a well field, an office building and laboratory, and a garage and mechanics facility.