Recovery of Heavy Minerals from Alabama Sand and Gravel Operations

摘要

A study was made of 25 samples from 15 Alabama sand and gravel operations to determine their heavy mineral content. All of the samples contained some heavy minerals (4 to 188 pounds per ton), and 80 percent contained 20 or more pounds of heavy minerals per ton of sand and gravel. Valuable heavy minerals, in order of decreasing amounts, were ilemite, kyanite, zircon, rutile, and monazite. Large-scale concentration tests were made on samples from three of the State's major producers. Gravity concentration by Humphreys spirals and tables resulted in bulk heavy mineral concentrates that graded from 87 to 91 percent heavy minerals. Mineral recoveries ranged, in percent, as follows: ilmenite, 60-95; zircon, 96-100; kyanite, 37-77; rutile, 89-100; and monazite, 96-100. Separation studies on a gravity concentrate from an eastern Alabama operation showed it would respond to conventional separation techniques to produce individual mineral concentrates. Individual mineral concentrates obtained were ilmenite, 58.7 percent TiO2; rutile, 93.7 percent TiO2; kyanite, 55 percent Al2O3; zircon, 58.0 percent ZrO2; and a rare-earth product containing 66.7 percent monazite and 7.1 percent xenotime. (Author)