Large quantities of alumina are produced yearly for the manufacture of metallic aluminum . In 1980, 90 percent of the raw material, bauxite, was obtained from foreign sources. Jamaica, Haiti, the Dominican Republic, Surinam, Guyana, Guinea, and Australia are the countries from which the United States imports this bauxite. Total consumption was 15.6 x 106 t, about 96 percent of this going to alumina production; smaller uses include abrasives chemical manufacture, refractories and ceramic fibers. The production of alumina may be divided into the following steps: Bauxite, a mineral containing about 55% aluminum oxide and less than 7% silica, is crushed wet ground to 100 meshes. The finely divided bauxite is dissolved under pressure and heat in Bayer digesters with concentrated spent caustic soda solution from a previous and sufficient lime and soda ash. Sodium aluminates is formed, and dissolved silica is precipitated as sodium aluminum silica. The undisolved residue (red mud) is se...