Uranium

Intro

Although uranium occurs in several areas of the state, much of the historic uranium and vanadium production is from numerous and relatively small mines in the Uravan mineral belt located in Mesa, Montrose, and San Miguel Counties. This area accounted for about 77% of the total uranium production in Colorado. The Uravan mineral belt mines produced almost 14 million tons of ore averaging 0.24 percent triuranium octoxide (U₃O₈) and over 356 million pounds of vanadium oxide. Uranium minerals formed irregular deposits in this area commonly referred to as roll-front uranium deposits. Vanadium typically occurs with uranium in these deposits. Most of these deposits are in sandstones of the Jurassic Morrison Formation. Roll-front deposits containing uranium also occur in other areas of the state like the Fox Hills Sandstone in Weld County. A different vein-type uranium deposit was mined in Precambrian gneiss and schist at the historic Schwartzwalder mine in Jefferson County. The Schwartzwalder was reportedly the single largest uranium mine in Colorado and produced 10.5 million pounds of U₃O₈ by 1978.

There are several uranium resources in Colorado including the Graysill property (vanadium and uranium), the Tallahassee Creek deposits in Park and Fremont counties, and the Maybell deposits in Moffat County as well as others. Although Colorado has been a producer of uranium in the past, there are currently no producing uranium mines or mills in Colorado. Uranium was last produced in Colorado around 2005 in Montrose County. Uranium reserves are abundant in Colorado and several companies continue to explore and maintain uranium mining permits in Colorado.

Although Colorado has been a producer of uranium in the past, there are currently no producing uranium mines or mills in Colorado. As of 2019, the proposed Pinon Ridge uranium mill located in Montrose County is on hiatus due to a 2018 court ruling. In 2019, uranium concentrate production from U.S. mines in 2019 was the lowest recorded since 1949. Uranium is listed as a critical mineral by the U.S. Geological Survey. In 2019, over 90% of uranium purchased and delivered to U.S. civilian nuclear power reactors came from other countries including: Canada (21%), Kazakhstan (18%), Australia (18%), Russia (15%), Uzbekistan (9%), and Namibia (5%). In July 2019, a presidential memorandum ordered the establishment of the U.S. Nuclear Fuel Working Group (NFWG) “to develop recommendations for reviving and expanding domestic nuclear fuel production.” In 2020, the NFWG announced a nuclear energy strategy which included strengthening the U.S. uranium mining and conversion industries and in early 2019, a federal judge lifted a ban on some uranium leases in southwest Colorado. The DOE Office of Legacy Management (DOE LM) restarted their uranium leasing program on uranium-rich public lands as it did in 2008. This program leases properties in the Uravan mineral belt area in Colorado. The DOE LM properties reportedly contain an estimated 13.5 million pounds of uranium resources and, as of July 2020, all the remaining tracts were leased.

Details

The U.S. is the world’s largest generator of nuclear power by far as of 2018—generating about 31.7% of total world nuclear energy, double the second-ranked country, France, and almost triple the third-ranked country, China. The nuclear share of the total U.S. electricity production in 2018 was about 19.3%. Uranium is used as a fuel in most U.S. nuclear reactors, however, most of that uranium must be imported. In 2019, over 90% of uranium purchased and delivered to U.S. civilian nuclear power reactors came from other countries. Uranium concentrate production from U.S. mines in 2019 was the lowest recorded since 1949. In 2019, U.S. uranium concentrate was produced from five in-situ leaching facilities, four in Wyoming and one in Nebraska, and one underground mine. So far, relying on imports has not been a significant problem for the country, but it could soon become a problem as more nuclear plants are built around the world, as world supplies become more constrained, and as future uranium prices rise.

Colorado does not host any nuclear power plants, however, several mining companies are interested in mining and milling uranium and associated vanadium deposits in the state. An elongated area located in Mesa, Montrose, and San Miguel counties contains the Uravan mineral belt. This area contains uranium and vanadium deposits generally in the Salt Wash Member of the Morrison Formation. This area was historically mined for both of these commodities and contained about 1,100 mines that ranged in size. Historically, these mines were managed on land leased by the Atomic Energy Commission (AEC) and now managed by the U.S. Department of Energy and U.S. Bureau of Land Management. Historic AEC leases have recently been leased again in 2019 for the future mining of uranium and/or vanadium. In 2019, vanadium was primarily (~94%) used for as an alloying agent for iron and steel. Future uses of vanadium for batteries may increase the current demand.

As reported in the CGS publication B-40 Radioactive Mineral Occurrences in Colorado and Bibliography, Jefferson County has been a major uranium producer in the state. The Schwartzwalder Mine, one of the major vein‐type uranium mines in North America, has produced approximately 98 percent of all U₃O₈ in the county. As of May 1978, total production from the mine has been reported as 10,500,000 pounds of U₃O₈ making the Schwartzwalder the largest single uranium producing mine in the state. Twelve other mines in the county have produced uranium, but only a small percentage compared to the Schwartzwalder’s total production. Seven of the ten uranium mines in the county occur where a fault or breccia zone transects the Precambrian Idaho Springs Formation. Some of these mines, including the Schwartzwalder, are all clustered along three northwest‐trending faults or breccia systems within six miles of the fault system along the Front Range.

Other areas of Colorado contain potential uranium resources. The Tallahassee Creek uranium deposits in Park and Fremont Counties are located within the Eocene Echo Park Alluvium and Oligocene Tallahassee Creek Conglomerate. Uranium mineralization in these units is above buried geologic structures within the area and is associated with carbonaceous material, pyrite, carbonate and secondary silica in sandstones and conglomerates interbedded with the Wall Mountain Tuff. Several deposits have been identified including the High Park, Hansen, Picnic Tree, Taylor (James-Taylor lease), and several others. Between 1957 and 1972, 95,400 tons of ore averaging 0.25% U₃O₈were mined, mostly from the Tallahassee Creek conglomerate. Some estimates by private mining companies indicate that the Hansen/Taylor deposit contains resources of 29,730,000 tons grading at 0.063% U₃O₈, or 37,480,000 pounds U₃O₈, and an inferred uranium resource of 43,681,000 tons with a grade of 0.058% U₃O₈ containing 50,443,000 pounds U₃O₈.

At the historic Graysill mining district in Dolores County, vanadium and uranium occurs in sandstones of the upper part of the Jurassic Entrada Sandstone just below its contact with the overlying Wanakah Formation. At the Graysill Mine, by 1971, 171 tons were mined at grades of 0.049% U₃O₈ and 1.907% V₂O₅ at the Graysill No. 1 Mine. At the Graysill No. 2, 31,778 tons were mined containing 0.08% U₃O₈ and 2.41% V₂O₅. Additional uranium and vanadium resources were mined in several other nearby areas within the Entrada Sandstone.

The Maybell uranium and vanadium deposits include tabular sandstone uranium deposits formed in locally tuffaceous, fluvial, arkosic sandstone in the Miocene Browns Park Formation. Uranium enrichment occurs mainly in the lower 150 feet of the Browns Park Formation in fine- to medium-grained sandstone that contains abundant clay in its matrix. The five largest producing mines of this district are the Rob Rollo Mine, the Marge Mine, the Gertrude Mine, the Sage-Buella Mine, and the Johnson Lease. Nearly 5,300,000 pounds of U₃O₈ have been produced from the Maybell mines over 28 years. Also, intermediate grade resources (0.01-0.05% U₃O₈) were identified in a two square mile area with an estimated 70 million tons of material in the Browns Park Formation containing 25 million pounds of uranium oxide. Also, there has been speculation that the Maybell area could contain at least 200 million pounds of uranium oxide in intermediate-grade resources. Shipments of ore totaling 48 tons and averaging 0.19 percent U₃O₈ and 0.10 percent V₂O₅ have been mined from the Sugar Loaf group.