A vast field of molybdenum below the surface of Bingham Canyon Mine has the potential to extend Rio Tinto's Kennecott Utah Copper mining operations there by years. But only time and more research will determine how much of the field is developed.

Right now, plans call for the mining operation at Bingham to close down in 2019, Kennecott superintendent of geology Gerry Austin told the Deseret News. "But as we find additional minerals and figure out how to mine it, that extends outward."

In the end, he says, "it comes down to the economics: how much can we sell it for; how much can we mine it for?"

Drilling work has identified a high-grade molybdenum deposit that extends as deep as 0.6 miles below the floor of the Bingham Canyon Mine pit and is believed to contain about 500 million tons of molybdenum. In summer 2008, Rio Tinto announced it would spend $270 million to build a facility to refine and process the silvery white metal, which is used primarily to strengthen steel alloys. But it's not yet clear whether mining the vast deposit will prove desirable, Austin said.

Kennecott has mined molybdenum — "moly" is the shorthand name — since the 1930s, breaking it out of the rocks from which the company is also extracting copper, said Jana Kettering, Kennecott spokeswoman. Rock removed from the mine is sent to a concentrator in Copperton, where the molybdenum and copper are separated from the other materials.

China is the biggest producer of the transition metal. There are three American mines that right now produce at least twice as much molybdenum as Kennecott does, Austin said.

If they go after the new deposit, it will likely be for its own sake, not as a byproduct. Moly may be looking at a promotion.

Kettering says that 0.5 percent of each rock load Kennecott now mines turns out to be copper. The molybdenum, in comparison, is about 0.04 percent. It is believed that the molybdenum Kennecott is considering going after is of higher grade, probably in the 0.1 to 0.15 percent range.

Molybdenum is sold by the pound and the price peaked around $40; it's currently around $15 to $18 a pound, Austin said.

Extending the mine's life is important to a lot of people, Kettering noted. There are 1,800 employees involved in the Kennecott mining operation. A University of Utah study said that each year Kennecott contributes $715 million to the economy through taxes, wages and other ways.

Kennecott has the techniques for mining at that depth and mine operations also tend to borrow good ideas and technologies "from what others have learned along the way," Austin said. So the big issue will probably not be how to mine it, but rather at what cost.

Kennecott each year produces about 300,000 tons of copper, 500,000 ounces of gold, 4 million ounces of silver and about 30 million pounds of molybdenum. It also produces 1 million tons of sulfuric acid as a byproduct of its smelting process.

e-mail: lois@desnews.com

Twitter: Loisco

Molybdenum

What it is: A silvery white metal

Commercial use: Primarily to strengthen steel alloys

Primary source: China

Melting point: 2,623 degrees Celsius (4,753 degrees Fahrenheit), the sixth-highest of all the elements. It will not burn at temperatures below 600 degrees Celsius (1,112 degrees Fahrenheit).

Biological use: Occurs naturally in tiny quantities in the human body and is believed to be part of many important biological processes.

Source: Wikipedia, American Cancer Society