LOVELOCK - Exploratory drilling and the search for more gold resumed last week at the dormant Relief Canyon Mine northeast of Lovelock. The work could expand potential resources, reveal higher grades of gold ore and attract additional investment in the mine.
"All you can do is drill and see what Mother Nature gives you back," Pershing Gold Corp. Manager of Exploration Douglas Prihar said. "We're chasing some past intercepts that were of higher grade material that averaged all over four grams or roughly one-tenth of an ounce per ton of ore."
High-grade deposits could justify the cost of underground gold mining but for now the plan is to resume surface mine operations at Relief Canyon next year, he said.
"If we were to find high-grade mineralization that was deep, it would have to be the right thickness and the right grade to support underground mining," Prihar said. "We still don't have enough information yet to fully determine whether we have material of that type."
The drilling company will complete 20 holes at an average depth of 600 feet with a total of about 10,000 to 12,000 feet, he said. Drilling locations are determined by underground fractures where gold may have flowed.
"We feel we've developed a better understanding of where the mineral's going, especially below cover, so we're using our new modeling to guide us there," Prihar said. "We're looking for faults and open fractures where a lot of the gold is deposited by fluids."
Tons of ore will be crushed and leached with a cyanide solution to extract the invisible gold dust using the existing leach pads at Relief Canyon. In the processing plant, gold and silver will be absorbed from the "pregnant" cyanide solution using activated carbon.
Finally, bars of the extracted metals will go to Utah for further refinement into jewelry grade gold and silver. At an average grade of
.02 ounces of gold per ton, it will take 8.5 tons of Relief Canyon ore to yield enough gold for an average man's wedding ring.
Prihar said a rock called "jasperoid" is a good indicator of gold deposits in Nevada and assays of the rock cores will help geologists further pinpoint the highest gold resources.
"Typically, here at Relief Canyon, some of the better grade material was in jasperoid," he said. "In this zone, we are definitely looking for its presence in the rocks, along with a few other minerals that are a good indication of when we're
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actually in the gold zone."
If gold prices remain high, small mountains of low-grade ore previously considered uneconomical may be worth processing after the mine re-opens next year, Prihar said.
"We're optimistic, but we're exploration geologists so we're always optimistic - we have to be," he said. "We're also realistic. If the gold price were to fall catastrophically the mine could be back-burnered until the economics improved."
The geologist described the some of the science behind modern gold prospecting and his fascination with the complex evolution of rocks and minerals over millions of years.
"We're still studying these rocks. They've had a long and difficult history," Prihar said. "Where the plates collide, they've been pushed up, squished, stretched and squished again. That's good for the structural preparation with a lot of fractured permeability for gold solutions. It creates a good environment for the gold to accumulate in those faults."
High-tech computer mapping of underground rock formations should still be secondary to old school, boots-on-the-ground geological detective work, according to Prihar.
"In many ways, the younger generations are so dependant on technology that the basic observational skills are being lost because they'd rather spend the time at the computer using GIS databases," he said. "It's what we call 'boot leather and a rock pick.' We walk, break a lot of rocks and record locations, textures, rock types, minerals and oxidation products. Those are the things we initially put in the sample bags for the assay lab."
Unlike old-time gold prospectors, most big-time gold mining in Nevada now depends on chemical analysis of ore to pinpoint invisible particles of the precious metal, Prihar said.
Accurate rock analysis in turn depends on skilled drilling techniques that deliver intact, well-catalogued core samples. West Core Drilling out of Elko has two shifts working 24/7 to complete this round of drilling out at the Relief Canyon Mine, Prihar said.
Operations manager Steve Tibbals said his company will have a new resource estimate for investors by the end of 2013 and a preliminary economic analysis in early 2014 based on the assay results of current exploration at Relief Canyon.
"I think it's a real positive thing for the company because so many others are pulling back," he said. "We've been fortunate enough to get the resources to push ahead full steam with our permitting efforts. We'd obviously like to see the prices to go higher, but we have every indication we can enlarge our resources with this drilling program."
Prihar said it's unlikely that any gold nuggets will be found at Relief Canyon. On the other hand, every rock in his office collection offers some valuable clues to the local geological history - even the pyrite or "fool's gold" brought in by a mine worker.
"We don't have any visible gold here," he said. "A lot of times when the guys are hiking around, they'll pick up rocks that seem interesting and bring them in."
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