Mica deposits of the Petaca district, Rio Arriba County, New Mexico

Wartime increases in demand for mica of strategic quality, beryllium, tantalum, columbium, tin, lithium, and uranium have focused attention on pegmatite deposits more sharply during recent years than ever before. Not only have numerous technical developments of the past few decades involved new uses for these commodities, but during the recent period of emergency these and other uses were greatly expanded. The attendant rapid increases in demand and a heavy dependence on foreign sources of supply soon confirmed the need for a careful appraisal of domestic resources of the minor pegmatite minerals. This need had been foreseen prior to 1939, when the Federal Geological Survey (GS) began a program of pegmatite investigations that attained nation-wide scope by the spring of 1942.