Modern gold mine gleams in Montana hills

Dan Banghart maneuvered his sport utility vehicle across rugged terrain, making sure to avoid 150-ton dump trucks that lumbered through the Golden Sunlight gold mine on a recent summer morning.

Big trucks, such as the ones he drove past, routinely haul stones from a deep mining pit to a crushing plant, where heavy machinery pulverizes rocks so that gold particles can be spun into bullion.

It’s an extensive operation that relies on blasting, oversized trucks, rock-crushing machines and toxic chemicals – all at a gold mine the size of which many Westerners are accustomed to. But in South Carolina, where a mine the size of the Golden Sunlight is preparing to open, people may be surprised at what lies ahead.

“There is a ‘wow’ factor,’” Banghart, the Montana mine’s general manager, said of those who see his company’s site for the first time.

To gain perspective on a large-scale gold mine, Banghart gave The State newspaper a tour of the mine this past summer, explaining how the operation works and what his company does to contain pollution and keep workers safe.

The Golden Sunlight’s main area of excavation, the Mineral Hill pit, was dug from the side of a mountain and is about three-quarters of a mile wide and 825 feet deep. The Golden Sunlight’s pit walls are terraced, giving the appearance of an ancient pyramid, to provide stability to the hole’s sides.

The Montana pit is about the same depth as what’s proposed for South Carolina’s new Haile Gold Mine, an operation that would become the largest open pit gold mine ever developed in South Carolina.

To get gold at the Golden Sunlight, workers use ammonium nitrate to blow up the pit floor. Once the pit floor has exploded, excavating equipment loads rock onto dump trucks. Ore, which contains gold, is trucked up a narrow dirt road that winds around the sides of the pit to the top, then hauled to a crushing plant.

“The trucks drive up slow, like 8 mph, out of the pit, up a 10 percent ramp,” Banghart said.

At the pit’s edge last summer, machinery resembling a large television satellite dish moved quietly from side to side. The radar equipment is one of two systems that track the stability of the mine’s walls, to make sure workers aren’t exposed to any potential cave-ins, Barrick officials said.

“These are determining whether there is any movement in the (pit) wall,” Banghart said, adding that the equipment is highly sensitive. “You see that dust coming off the wall up there? It would be picking that up.”

The pit at the Golden Sunlight is uneven, meaning it has a high wall and a lower one where the mine’s radar machinery is located.

Waste rock dug from the pit has filled an entire valley between two peaks. The filled area is easily visible from Interstate 90 between the tiny towns of Whitehall and Cardwell.

The waste rock is capped by dirt and grass in an effort to prevent water from seeping in and releasing sulfuric acid. Grassy areas have begun attracting wildlife, including a small herd of deer that moved through the area on a breezy summer day.

Barrick Gold Corp., one of the world’s largest gold mining companies, says its mine near Whitehall is actually small by western standards. Many gold mines in Nevada, the nation’s top gold-producing state, are thousands of acres larger than the Golden Sunlight in the minerals rich area between Reno and Salt Lake City, Utah.

Like some other gold mines, the one at Whitehall takes rock from its pit to a crushing plant and then to a gold processing mill.

As Banghart walked inside the mill last summer, he encountered rows of steel machinery that rattled and churned, creating enough of a racket to make hearing difficult. Huge vats of a watery solution vibrated, shaking liquid in the metal containers. Lights blinked on the walls of a control room full of dials, knobs and computer screens.

Banghart said an employee who staffs the control room must keep constant watch on how much material flows through the plant and whether the processes are being followed. In the control room, the operator can make changes in how fine to grind rock or how much cyanide should be put into rocks that are processed for gold.

The metal milling plant beats already-crushed rock so mercilessly that it transforms into a material resembling baking flour. Then, cyanide and lime are mixed with the gold-bearing rock in tanks to separate out the precious metal. The process is akin to dissolving salt from salt water, company officials said.

The plant then turns the material into impure gold bars, which contain about 30 percent silver. Waste cyanide that can’t be reused is disposed of in the Golden Sunlight’s tailings pond. While potentially deadly, cyanide is considered by many to be the best substance to separate gold from rock.

That pond is a vast shallow lake held back by an earthen and rock dam. Unlike in days past, cyanide that goes into the pond is less toxic because the Golden Sunlight has a destruction process to neutralize the material, Barrick Gold officials say.

Banghart said the mining process his company uses is far different from the old days, when prospectors dug sizeable gold nuggets from rivers.

“It is microscopic gold,” he said. “We are basically getting the gold at a molecular level through chemistry.”

This story was originally published October 11, 2014 at 6:16 PM with the headline "Modern gold mine gleams in Montana hills."