Molybdenum mining in the United States produced 65,500 metric tons of molybdenum in 2014, worth US$1.8 billion. The US was the world's second-largest molybdenum producer, after China, and provided 25% of the world's supply of molybdenum.
The US was a major exporter of molybdenum; net exports made up 48% of US production. Because most molybdenum is used as a steel alloy, demand for, and therefore the price of, molybdenum, tracks the demand for steel.
As of the end of 2014, the United States had 2.7 million tons of molybdenum reserves, and 5.4 million tons of identified molybdenum resource.[1]
Molybdenum is produced in the US from porphyry deposits of two types. The first class, which produces molybdenum as the primary product, includes molybdenum porphyry deposits. In 2014, three such molybdenum porphyry deposits were mined: two in Colorado and one in Idaho; the mine in Idaho was put into inactive status at the end of 2014. The second class, which produces molybdenum as a byproduct of copper mining, includes copper porphyry deposits. In 2014, byproduct molybdenum was produced at ten porphyry copper mines, in Arizona, Montana, Nevada, and New Mexico. Byproduct molybdenum from copper mines accounted for 47% of US molybdenum production in 2013.
In both molybdenum porphyries and copper porphyries, the molybdenum is present as molybdenite.
The Climax mine, historically the world's largest source of molybdenum, is north of Leadville, Colorado. Climax first produced molybdenum in 1915, and was worked continuously from 1924 until it was shut down in 1995. Formerly an underground mine, the Climax mine reopened as a surface mine in 2012. It is owned by the Climax Molybdenum Company and now operates as an open pit.
The Henderson molybdenum mine, near Empire, Colorado, started producing molybdenum in 1976, and was the nation's leading molybdenum producer in 2013, with 13,600 metric tons of molybdenum. The mine is owned by Climax Molybdenum Company
The Thompson Creek mine, in Custer County, Idaho, is owned by the Thompson Creek Metals Co., Inc. The mine was a large producer in 2014, but was put on inactive status in December 2014.[2]
As of 2014, there were ten US copper mines producing molybdenum as a byproduct. The number of mines producing byproduct molybdenum at any given time depends on the price of molybdenum and the amount of molybdenite in the ore.
Both copper sulfides and molybdenite are separated from the gangue by froth flotation. To separate the molybdenite from the copper sulfides, the copper/molybdenum concentrate is run through a molybdenite recovery flotation circuit, in which chemicals are added to "depress" the copper, meaning to prevent the copper sulfide minerals from attaching to the froth, while the molybdenum is unaffected. A few plants do the opposite, adding other chemicals to depress the molybdenum while the copper floats.[3]
There are a number of undeveloped and currently inactive molybdenum deposits in the United States.
Inactive mines
Deposits not yet mined
The United States dominated molybdenum production for most of the 20th century, producing more than half the world's production each year from 1925 through 1981. In 1953, US mines supplied 92 percent of world molybdenum production.[6] The US was the world's leading molybdenum producer from 1924 through 2006, after which US production was overtaken by China.