Strategic Metals (Tantalum, Columbium, Beryllium) in Pegmatites of Copper Mountain, Fremont County, Wyoming. A Preliminary Report

摘要

In 1987 and 1988, the Bureau of Mines evaluated pegmatites and granitic rocks on the south side of Copper Mountain, Fremont County, WY, primarily for the strategic metals tantalum, columbium, and beryllium. The U.S. relies on foreign imports for over 90% of the tantalum and columbium consumed annually, and has no major known tantalum deposit. Widely spaced reconnaissance sampling identified subeconomic tantalum resources in two pegmatites on Copper Mountain, amounting to 1.5 million short tons at grades of 0.02% to 0.03% Ta2O5 (tantalum pentoxide). Tantalum content is 0.8 million pounds of Ta2O5, or about 1/5 of the total tantalum resources delineated in the U.S. Tantalum recovery testing showed that 70% recovery is possible. Additionally, columbium and beryllium could be byproducts of tantalum mining. Tungsten, gold, silver, and copper, primarily in quartz veins, are not present in economic amounts. Sample assays suggest additional tantalum resources could be present in other pegmatites in the study area, but more sampling work is required to determine resources. Unsampled pegmatites on an adjacent 2 square miles of land should be examined. Discovery of more tantalum resources could help alleviate U.S. dependence on foreign imports.