Heavy Mineral Sands
Sedimentary deposits of sand, silt and clay often contain a small percentage of heavy mineral grains that have a higher specific gravity (greater than 2.9) than the more common quartz sand grains (about 2.65). Some are easily visible as dark and opaque grains, but others are light-colored or translucent and not as easy to distinguish from quartz. Heavy minerals include magnetite, ilmenite, leucoxene, rutile, zircon, garnet, monazite, among others. Some of these are valuable industrial minerals containing titanium, zirconium, alumina, and rare earth elements. Derived from the weathering of igneous and metamorphic rocks exposed in inland regions, heavy minerals can be concentrated by coastal, alluvial, and eolian processes that carry away the less dense grains, leaving behind the denser heavy mineral sands.Year of first production in Virginia: 1991
Location of first production in Virginia: Dinwiddie County
Ilmenite (FeTiO3), leucoxene (altered ilmenite), and rutile (TiO2) contain titanium dioxide which is primarily used for the manufacture of white pigment used in paint, plastic, and paper. Rutile is also a source of titanium sponge metal used in steel alloy for applications in the aerospace industry, artificial joints and limbs, and heart pacemakers. Zircon (ZrSiO4) is a source of the element zirconium used in a variety of industrial chemical applications, as a ceramic glaze, and in refractory bricks and foundry sand in steel manufacture. Monazite (CePO4) typically contains natural admixtures of rare earth elements including cerium (Ce), lanthanum (La), neodymium (Nd), praseodymium (Pr), among others. These elements are used in energy generation, the manufacture of electronics, batteries and magnets, and a wide variety of other metallurgical applications. All of the minerals and contained elements listed above are among the draft list of 35 materials that are considered "critical to national security" by the U.S. Government.
Economic deposits of heavy minerals may be found in modern sediment accumulations as well as in ancient beach deposits that may be far inland from today's shorelines. In Virginia, Iluka Resources Ltd produced titanium and zirconium concentrates at the Old Hickory and Concord deposits in Dinwiddie County, and at the Brink operation in Greensville County. These heavy mineral deposits formed in beach and dune sands about 3 to 4 million years ago during the Pliocene Epoch, when the Atlantic Ocean shoreline was at a higher elevation near the present location of Richmond.
Ilmenite, leucoxene, rutile, and zircon make up approximately 80 percent of the heavy mineral concentrates produced by Iluka. The mined sediments were processed through gravity spiral concentrators to separate the denser heavy minerals from the lighter density non-economic mineral grains. Electrostatic and magnetic separation further concentrated the individual heavy mineral constituents. In 2017, Iluka suspended operations, but continues to hold mining leases in these areas.
Annual production reported by mine operator
Bedinger, G.M., 2018, Titanium: U. S. Geological Survey 2015 Minerals Yearbook, p. 79.1-79.15
Bedinger, G.M., 2017, Zirconium and Hafnium: U. S. Geological Survey 2015 Minerals Yearbook, p. 86.1-86.7
Department of the Interior, 2018, Draft List of Critical Minerals: Federal Register, Vol 83, No 33, February 16, 2018, p. 7065-7068.
Gilmer, A. K., Enomoto, C. B., Lovett, J. A., and Spears, D. B., 2005, Mineral and fossil fuel production in Virginia (1999-2003): Virginia Division of Mineral Resources Open-File Report 05-04, 77 p.
Virginia Division of Mineral Resources, 1993, Geologic Map of Virginia: Virginia Division of Mineral Resources, scale 1:500,000.