Approximately 22.7 million metric tons (25 million short tons) of heavy minerals, at an average grade of 6 wt percent in 377.8 million metric tons (416 million short tons) of sand, have been delineated in 19 deposits in the upper Coastal Plain of North Carolina and Virginia. Average concentrations of the principal minerals are ilmenite 60 percent, rutile 2.5 percent, zircon 12.5 percent, staurolite 8.5 percent, tourmaline 0.7 percent, kyanite 3.0 percent, sillimanite 1.3 percent, and others (principally limonite) 11.5 percent.These deposits formed during a worldwide, Pliocene, transgressive-regressive event that occurred between 3.5 and 3.0 Ma. The deposits formed as beach or dune sands during the regressive phase of the event over an elevation range of 96 m (315 ft) to 53 m (175 ft).Other major deposits that are interpreted to have formed during the Pliocene transgressive-regressive event are as follows: Trail Ridge, Florida; Enneaba, Western Australia; Lakehurst, New Jersey; and deposits of the western Murray basin, Victoria, Australia. Combined reserves of these Pliocene deposits exceed 317.5 million metric tons (350 million short tons) of heavy minerals. The potential for new discovery of Pliocene deposits elsewhere in the world is judged to be favorable.