Uranium is a dense, heavy, metallic element (atomic number 92 on the periodic table) that occurs naturally in over 200 mineral forms within rocks, soils and water. Typically found in very low but variable concentrations ranging from less than 1 part per million (ppm) to about 8 ppm, uranium in the Earth’s crust averages about 2.5 ppm while the concentration in seawater is about 0.003 ppm. Uranium is a trace element in many of the common rock-forming minerals, but is also found in ore minerals such as uraninite (uranium oxide), coffinite (uranium silicate), among others. With a specific gravity of about 18.7, natural uranium is nearly as heavy as gold (about 19.3). The known physical properties and geochemical “behavior” of natural uranium are good predictors of how the element will be distributed in rock-forming minerals and within the various geologic settings of the Earth’s crust. Uranium is naturally radioactive, meaning that it spontaneously decays through a series of so-called “daughter elements” to form the stable element lead (atomic number 82). During the decay process, uranium and the daughters emit characteristic patterns of alpha and gamma radiation, which even at very low levels can be measured and used to map the variable background concentrations within rocks and soils.
Uranium in nature exists in several isotopic forms, such that the nucleus of the uranium atom contains 92 protons, but a variable number of neutrons, which together add up to the atomic mass. The main isotopes are U-238, U-235, and U-234. Most of the weight of natural uranium consists of atoms of U-238 (99.3%), while U-235 (0.7%) constitutes most of the remainder, and U-234 (0.006%) only a very small amount. That U-235 is naturally fissionable, meaning that the nucleus may be split with a consequent release of energy, makes this specific isotope valuable today as a fuel in nuclear power generation.
Historic Uses of Uranium
In the past uranium was commonly used as a colorant in ceramic glazes and glass with colors ranging from orange-red to yellowish-green. The element has been used as an oxide catalyst in the production of plastic as well as in the electrical industry for the manufacture of UV light electrodes and resistors in incandescent lighting. The use of uranium compounds by early photographers in the mid 1800s led to the discovery of spontaneous radioactivity.
Uranium Geology and Resources
Geochemical sampling and mapping of natural radioactivity by aerial and ground survey methods has greatly assisted in our understanding of the distribution of uranium-enriched bedrock in Virginia. In the Blue Ridge and Piedmont provinces, these formations typically include silica-rich meta-igneous rocks such as granite, alkali-rich plutonic rocks, and pegmatites. In the Valley and Ridge province, carbonaceous black shales often contain relatively elevated uranium content. Similar uranium enrichment in black shales deposited in the Mesozoic basins has also been noted. Uranium enrichment may also be associated with the deposition of phosphorites in the Coastal Plain. Surface weathering of these rocks may provide sources for mobile uranium (for example, uranium-bearing minerals entrained in the sands of stream sediments), yet the natural processes that concentrate uranium-bearing minerals in potentially mineable deposits are complex and have occurred very rarely in geologic time.
Geologic bedrock formations with naturally elevated background concentrations.
Source: State Geologic Map of Virginia (1:500,000)
The earliest exploration in Virginia for uranium and associated minerals began in the early 1950s. A publication entitled “Uranium in Virginia” (Stow, 1955) describes the interest at that time in finding uranium in Virginia. Based upon the known models of uranium deposits at that time, the greatest potential for discovery of commercial resources was considered to be in the western portion of the state. In the late 1970s and early 1980s, the National Uranium Resource Evaluation (NURE) program was conducted under the federal Atomic Energy Commission, exploring areas throughout the eastern U.S. for evidence of radionuclides. The program employed exploration techniques such as aerial radiometric surveys, stream sediment sampling and other surface measurements. The results of these studies helped set the foundation for mapping the distribution of uranium-enriched bedrock in Virginia.
NURE aeroradiometric data showing color-shaded eU (ppm).
Source: USGS OFR 2005-1413
During this time, several mining companies conducted uranium exploration programs and land leasing in Virginia, most notably resulting in the discovery of the Swanson deposit by Marline Uranium Corporation at Coles Hill in 1978. Marline drilled approximately 256 exploration holes at Coles Hill between 1980 and 1982.
In 1982, Virginia enacted Title 45.1, Chapter 21 of the Code of Virginia which governs uranium exploration and also included a moratorium on uranium mining, requiring that a program to regulate mining be established by statute before the Commonwealth could accept uranium mining permit applications. The moratorium remains in place today. In 1983, the Uranium Administrative Group (UAG) was created and authorized to contract with consultants to conduct studies evaluating the costs and benefits of uranium mining at specific locations in Pittsylvania County, and report its findings to the Virginia Coal and Energy Commission in December 1983. In January 1984, the Coal and Energy Commission accepted the UAG recommendation to continue and expand the scope of studies under the oversight of the newly created Uranium Task Force (UTF), which reported its findings on October 1, 1984 (final report). Not long after that report was released, the market price for uranium decreased substantially and the outlook for future demand appeared to be limited. Based on anticipated production costs, the Coles Hill deposit was no longer considered a viable commercial mining enterprise and Marline Corporation dropped their mineral leases.
In 2005, uranium prices begin to increase and interest in the Coles Hill site was renewed. In 2007, Virginia Uranium, Inc. (VUI) applied for and received an exploration permit to further explore the Coles Hill deposit. The general requirements of the uranium exploration statue are found here.
Legislation was introduced in the 2008 session of the General Assembly to establish a legislative commission to consider whether uranium mining should occur in the Commonwealth. As a result, several studies were conducted to review public health and environmental issues associated with uranium mining and milling culminating in the 2012 report issued by the Uranium Working Group that included staff from DMME, the Department of Environmental Quality (DEQ) and the Virginia Department of Health (VDH). For more information concerning these studies, please visit the archived UWG website.
Bailey, W.M., 1984, Uranium and Thorium Mineralization of the Northern Half of the Horseshoe Mountain Quadrangle, Nelson County, Virginia: Virginia Division of Mineral Resources Virginia Minerals, v. 30, n. 4, p 37-46.
Baillieul, T.A. and Daddazio, P.L., 1982, A Vein-Type Uranium Environment in the Precambrian Lovingston Formation, Central Virginia: Virginia Division of Mineral Resources Publication 038, p 1-12.
Henika, W. S., Thayer, P.A, 1983, Geologic Map of the Spring Garden Quadrangle, Virginia: Virginia Division of Mineral Resources Publication 048, scale 1:24,000.
Johnson, S.S., 1979, Radioactivity Surveys: Virginia Division of Mineral Resources Virginia Minerals, v. 25, n. 2, p 9-14.
Johnson, S.S., 1991, Natural Radiation: Virginia Division of Mineral Resources Virginia Minerals, v. 37, n. 2, p 9-14.
Johnson, S.S., Gathright, T.M., and Henika, W.S., 1979, Gamma-Ray Spectrometry and Geologic Mapping: Virginia Division of Mineral Resources Virginia Minerals, v. 25, n. 3, p 17-23.
Krason, J., Johnson, S.S., and Marr, J.D., 1988, Geochemistry and Radioactivity in the Powhatan Area, Virginia: Virginia Division of Mineral Resources Publication 078, p 1-60.
Lasch, D.K., 1988, On Radon: Virginia Division of Mineral Resources Virginia Minerals, v. 34, n. 1, p 1-4.
Le Van, D. C., 1990, Energy Resources and Facilities in Virginia: Virginia Division of Mineral Resources Publication 100, scale 1:500,000.
Marr, J. D., 1984, Geologic Map of the Pittsville and Chatham Quadrangles, Virginia: Virginia Division of Mineral Resources Publication 049, scale 1:24,000.
Stow, M.S. 1955, Uranium In Virginia: Virginia Division of Mineral Resources, Virginia Minerals, v. 1, n. 4, p 1-4.