Western North Dakota contains several areas of known radioactive mineral deposits. Investigations done from the late 1940s to the late 1970s discovered several large areas of increased radioactivity in Bowman, Slope, Stark, Billings, and Golden Valley counties. There are at least 21 areas in western North Dakota that contain uranium, primarily within lignites, sandstones, or carbonaceous mudstones.
Uranium exploration began in North Dakota in 1948. Uranium and other radioactive elements were often found associated with beds of lignite. These low-grade ore deposits often ranged from 0.005 to 0.2 percent uranium. It is theorized by many geologists that these radioactive elements were released during the alteration of volcanic glass. These radioactive elements were then leached by groundwater into the underlying rocks until a change in pH and or Eh caused them to precipitate, often in a coal or organic-rich lenses in sandstone. Early on it was noted that radioactive lignites often were overlain by sandstones.
Discovery of uraniferous lignite deposits in western North Dakota by federal scientists led several energy companies to explore for uranium in western North Dakota during the 1950s. Beginning in 1956, a few hundred tons of uraniferous lignite was shipped from North Dakota to processing plants. The mills were set up to process uraniferous sandstones and had difficulty processing the low-grade ore lignites. Beginning in 1962, this problem was rectified by burning the uraniferous lignite in pits at the mine site, often by burning the bed in place after the overburden had been removed. The process reportedly took from 30 to 60 days and diesel fuel and old tires were often mixed with the lignite to assure that it would burn sufficiently. The ash from the mines was then sent to Belfield or Griffith where it was further reduced by burning in kilns. The resulting ash was then shipped to mills in South Dakota, Colorado, and New Mexico. Uranium mining took place in southwestern North Dakota from 1962 to 1967 (Karsmizki, 1990). At least seven, and possibly as many as fourteen uraniferous lignite mines operated in the state in the 1960s. We will likely never know the exact number of mines because records were poorly kept for several reasons including national security, and most were relatively small, short-lived operations. Typically, these mines were shallow pits excavated to the top of uraniferous (uranium-bearing) lignites. Mining was discontinued in 1967 after a total production of approximately 85,000 tons of ore resulting in 270 tons of "yellow cake" (U3O8).
Renewed interest in uranium in the mid-1970s resulted in several uranium investigations centered in the Chalky Buttes (Slope County) and Gascoyne (Bowman County) areas. In 1976, mineral companies renewed uranium exploration activities in western North Dakota when uranium prices reached $40 per pound. Between 1976 and 1980, the ND Geological Survey issued 22 uranium exploration permits and companies drilled almost 1,400 exploration holes. Most of these holes were drilled in Slope, Bowman, Adams, Billings, and Stark counties.
The accident at the Three Mile Island nuclear plant in Pennsylvania in March of 1979 effectively halted all uranium exploration in the United States. Orders for new power plants ceased and most uranium exploration in the region came to a standstill as many energy companies disbanded their mineral divisions.
While any future uranium mining in North Dakota is speculative, what is clear is both the federal government and the State of North Dakota have much more stringent environmental laws than were in effect five decades ago. These laws would protect the health and safety of the miners as well as local landowners.
Selected References for North Dakota Uranium
Beroni, E.P. and Bauer, H.L., Jr., 1952, Reconnaissance for uraniferous lignites in North Dakota, South Dakota, Montana, and Wyoming: United States Atomic Energy Commission, Technical Information Service Extension, TEI-123, 93 p.
Denson, N.M., Bachman, G.O., and Zeller, H.D., 1959, Uranium-bearing lignite in northwestern South Dakota and adjacent states: United States Geological Survey Bulletin 1055-B, p. 11-57.
Denson, N.M. and Gill, J.R., 1965, Uranium-bearing lignite and carbonaceous shale in the southwestern part of the Williston Basin - a regional study: United States Geological Survey Professional Paper 463, 75 p.
Karsmizki, K.W., 1990, U3O8, Uranium industry context statement: prepared for UNDAR-West by Western History Research, Bozeman, Montana, 79 p.
Moore, G.W., Melin, R.E., and Kepferle, R.C., 1959, Uranium-bearing lignite in southwestern North Dakota: United States Geological Survey Bulletin 1055-E, p. 147-166.
Murphy, E.C., 2007, Uranium Deposits in Southwestern North Dakota: North Dakota Geological Survey Geologic Investigation No. 40. GI-40
Murphy, E.C., 2007, After an Absence of Nearly 30 Years, Interest in North Dakota's Uranium Deposits is Back: Department of Mineral Resources Geo New Newsletter, vol. 34, no. 2, p. 1-4.
Murphy, E.C., 2008, Uranium Exploration Permits Issued: Department of Mineral Resources Geo News Newsletter, vol. 35, no. 2, p. 12.
Murphy, E.C., 2011, Spikes on gamma ray logs southwestern North Dakota: North Dakota Geological Survey Geologic Investigation No. 138. GI-138
Murphy, E.C., 2011, Uranium concentrations in groundwater southwestern North Dakota: North Dakota Geological Survey Geologic Investigation No. 139. GI-139
Murphy, E.C., 2015, Uranium in North Dakota: North Dakota Geological Survey Geologic Investigation No. 184, 47 p. GI-184
Noble, E.A., 1973, Uranium in coal, in Mineral and water resources of North Dakota: North Dakota Geological Survey Bulletin 63 p. 80-85.