Alumina From Alunite - Domestic Resources

Most of the aluminum produced in the United States today is derived from foreign bauxite deposits. Earth Sciences, Inc. initiated a program to evaluate domestic non bauxite sources for alumina in the 1960's. In the initial evaluation of alunite, domestic resources were not sufficient to support development. An exploration program led to the discovery of large deposits of alunite in Utah and several other western states. Identification of alunite is difficult as both its physical and chemical characteristics are similar to the minerals with which it is associated. Most of the significant alunite deposits in the western United States are replacement type deposits. These deposits have formed as a result of hydrothermal alteration of volcanic, sub-volcanic, and igneous rocks. Typical alunite deposits contain between 30 and 50% alunite and 50 and 70% quartz, with minor amounts of other minerals. Four mineralogical zones are common in these systems. They include a siliceous zone, a quartz-alunite zone, a kaolinite zone, and a chlorite-montmorillonite zone. Total US reserves of alunite were estimated at 20 Mt fat 30% alunite) by the US Bureau of Mines in 1941. More recent work by the US Geological Survey estimates reserves of 252 Mt and potential resources at 1.4 Gt. Reserves and resources estimated for 23 properties on which field work has been done by ESI are considerably higher. Most of these properties have reserves and potential resources of several hundred million metric tons. The combined demonstrated reserves of these properties are estimated to be about 650 Mt. Inferred reserves are estimated at 2.5 Gt and potential resources at 8 Gt. It appears that the US has sufficient reserves and resources for alunite to be considered as a potential nonbauxite source of alumina.