More than a half-mile below the surface of Red Mountain in the Colorado Rockies, it's a typical workday for Justin Whetton. He spends most of his 12-hour shift operating a gigantic loader inside a dark tunnel, scooping over 300 buckets of rock a day, hauling it from one shaft and dumping it down another where it falls into huge trucks that take it to a powerful underground crusher.
Whetton makes around $20 an hour for his labor, but each scoop of ore, weighing 10 or 11 tons, is worth $1,000. The value comes from a metal inside the rock, called molybdenum. About 44 lbs. of "moly," as it's known in the industry, is contained in each bucket Whetton moves at the Henderson Mine.
The mine, located below Berthoud Pass near Empire, Colo., is the largest primary molybdenum source in the world. Its owner, Climax Molybdenum, is a subsidiary of Phelps Dodge Corporation, the world's second-largest producer of molybdenum and copper after Codelco, Chile's state-owned mining company. Last year Phelps Dodge produced about 9 percent of the world's moly supply, some 28 million pounds, most of it coming out of Henderson's vast lode.
The Ted Scripps Fellows got a close-up look at a major underground mining operation when they visited Henderson on April 22. Donning hard hats, headlamps, safety goggles and a self-rescuing device designed to provide breathable air in the event of a mine emergency, the fellows and CEJ staff descended some 3,000 feet in a shaft elevator into the bowels of Red Mountain.
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| Ted Scripps Fellows deep inside Henderson Mine (Photo/Andrew Silva) |
Here, as if inside a giant subterranean maze, they boarded tractors that negotiated a warren of tunnels to give them an overview of some of the world's most sophisticated hard-rock mining operations. In the process, they learned a lot about a metal called moly.
While many people have never heard of molybdenum, let alone tried to pronounce it, they have almost certainly benefited from its use. Chemical-grade moly, the pure form mined and milled at Henderson, is used for many industrial purposes. It makes pipelines more corrosion-resistant, acts as a smoke retardant for plastics, and is used in CO2 detectors, fluorescent light bulb tubes, computer heat sinks, and in the orange paint pigment bought by the U.S. Navy.
However high-grade moly is best known as a lubricant. It's used in the manufacture of lower-friction piston rings in the automotive industry, as a spray for bicycle chains, and is added to greases and oils. In Europe, where automobile oil has a higher moly content, you only need to change your car's oil every 15,000 miles, Mine Manager Kurt Keskimaki said, adding that such oil is expected before long in the U.S.
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| Fellow Nadia White talks to Mine Manager Kurt Keskimaki (Photo/Andrew Silva) |
Moly is also used as a catalyst for getting rid of sulfur in petroleum refining, an important function in meeting clean-air standards. In fact, about half of the moly mined at Henderson goes to Houston where it's processed by Criterion, a division of Shell, which is a major buyer.
Production at Henderson began in 1976, following the ore body discovery in 1964. Initially found by Uranium Research and Development, or URAD, who thought it was uranium ore, it turned out to be molybdenum, an enormous deposit. Geologically, it was the perfect set of circumstances, 13 different mineralizing events that kept enriching the deposit with more layers of the purest moly in the world.
It's hard to get a handle on just how much of the mineral makes up the core of Red Mountain, but Keskimaki has the figures: "We sit on 166 million tons of moly ore, 600 million pounds of recoverable moly."
Shaft sinking commenced in 1968. Initial removal began at the 8,100-foot level, but current extraction is now at 7,210 feet. A quarter-million feet of long hole are drilled each year, using more than a million pounds of explosives. Once the ore is crushed at the bottom level of the mine, it's sent on a conveyor belt one mile up to the surface, then 14 miles further on the belt to the mill site across the mountains in the Williams Fork Valley.
Fellows and CEJ staffers marveled at the complex operation as they stood above the gyrating crusher on the mine floor, watching as 80-ton haul trucks, the biggest underground trucks in the world, dumped their load of rock into the crusher's bowl. Like a giant mortar and pestle, the device crunched the ore chunks into pieces of rock 4-8 inches in diameter, small enough to load onto the conveyor belt that whisks the ore over to the mill at about 50 mph. The process was noisy enough that the visitors were glad to have the earplugs provided, and at times the face masks necessary to cut the dust and exhaust that are inescapable amid such operations, despite mitigation efforts.
Mine ventilation is just one aspect of the Climax company's commitment to worker safety. "We move more tons of air in a day than tons of rock," said Keskimaki. That's a lot of air, since 21,300 tons of material are milled daily at Henderson.
Such complex ventilation systems are part of the reason why Henderson is Colorado's second biggest power user after Pueblo's steel mill. The mine and mill, which operate around the clock, use 47 megawatts a day for an average monthly energy bill of $1.5 million – less than half the steel mill's cost. Fellow Sam Eaton said he was "amazed at the amount of energy they use. It's mind-boggling."
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| Fellows "journey to the center of the Earth" (Photo/Andrew Silva) |
The conveyor belts are also power-hungry components of the Henderson enterprise, using 11,000 hp engines to transport the ore uphill to the mill. There, it is processed by separating the moly from its granite casing. First, the host rock is ground down into particles as fine as beach sand. During the milling, water and reagents are added, the latter causing molybdenum particles to float when the slurry is mixed with air. The moly adheres to the bubbles, allowing the metal to be separated from its host. More grinding and flotation further refines the moly concentrate, which at this point resembles ultra-fine, powdery graphite, very shiny and dark gray. In its final form as it leaves the mill, the moly is concentrated to nearly 250 times what it was when it entered as incoming ore. The process doesn't end here, though: the concentrate is filtered, dried and packaged for shipment by truck to further processing plants in Iowa, England and the Netherlands.
What's left over are the slurry remains and ore tailings. These are transported to the 1,000-acre tailing area where the moly-free granite settles and the water goes through an extensive reclamation process to be reused in a closed system at the mill.
Fifteen miles away, the mine sits near the head of the Clear Creek watershed, a region of alpine meadows and crystalline streams. Dealing with industrial wastewater is thus Henderson's biggest environmental stewardship issue. Fellows got a close-up look at the company's state-of-the-art treatment plant built in 1997, which handles up to 1600 gallons per minute from the mine. A million gallons a day are pumped into the plant from underground.
Ridding the water supply of toxic levels of manganese and zinc is the primary goal of the treatment facility. Tony Lucero, Henderson's environmental coordinator, called this "the most prominent operation we deal with from an environmental standpoint."
Calcium oxide is used to raise the pH-level of the water to precipitate out the minerals, which are removed and trucked to the BFI landfill between Golden and Boulder. Sulfuric acid is then added to lower the pH before the water is discharged into Woods Creek.
The company has been so successful that a trout fishery thrives in the stream below the discharge site, and the city of Golden buys Henderson's reclaimed water for its drinking water supply.
Fellow Nadia White appreciated the chance to see Henderson's operations and environmental mitigation up close. "I always find it valuable to go to the site of large industrial activity to get a sense of the scope and the potential economic impact, and the economic contribution to a community."
Even moving millions of pounds of rock a day, Keskimaki estimates there are enough reserves still inside the Red Mountain lode – about 1.5 billion pounds -- to keep Henderson operating for 20 more years.
A building boom and demand for petroleum products in China is keeping current moly demand high, he said, as well as speculation that a parallel Alaska pipeline might be built if additional oil drilling is approved in the Arctic. But eventually the mine's rich reserves will be exhausted. When that happens, a major reclamation effort will be required on Henderson's 12,800-acre site.
Lucero said the most significant reclamation work will take place at the mill, where tailings will be removed and wetlands and dry islands created. The company is working already to thin scruffy forests near the mill where weak trees have succumbed to a pine bark beetle outbreak, leaving vast mountainsides of dead and dying trees.
As for the fate of the mine, it may have a sci-fi future. Keskimaki said Henderson is in the running to be a deep underground laboratory for nuclear physicists to study subatomic particles called neutrinos. Since cosmic rays above the Earth's surface can interfere with neutrino behavior, scientists need to observe them by blasting them at high speeds thousands of feet below ground, shielded by a deep rock overburden. Just thinking about it makes the moly mining process seem downright simplistic.
Keskimaki thinks the odds are good that Henderson could be selected, given its proximity to a major airport and the Denver metropolitan area. In the meantime, mining moly by the thousands of tons continues, out of view of the backcountry skiers and hikers and fishermen who frequent the high country above the mine's expansive underworld.
Check out these Web sites for more on the Henderson Mine, NSF plans to build a deep underground neutrino lab, and what neutrinos are and why scientists want to study them.
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