National Geographic : 1978 Aug
Hungry for aluminum but lean on rich bauxite deposits, the United States digs into its own backyard for other alumina bearing substances. There's no shortage: Constituting 8 percent of the earth's crust, aluminum is the most abundant of metals, as well as one of the hardest to produce. To manufacture aluminum, you must first have alumina. Billions of tons reside in kaolin in Geor gia, anorthosite in Wyoming, alunite in Utah. Because these materials contain less alumina than bauxite does, the problem is to find ways to process the metallic ores economically. In Boulder City, Nevada, a U. S. Bu reau of Mines miniplant-bigger than a laboratory, smaller than a production unit -s e eks an economically feasible process for freeing alumina from kaolin (right).