Abstract: A suite of 50 rock specimens, collected by the 1947 Washburn Mount McKinley Expedition, was scanned radiometrically. The maximum radioactivity observed in any one of the specimens was about twice background. Radiometric analyses of the most radioactive samples show that a sample of vein quartz coated with manganese oxide contains 0.009 percent equivalent uranium and that the maximum equivalent uranium content of granitic rock types is .004 percent. The radioactivity of the manganese-stained quartz is probably due to traces of uranium in the manganese mineral, whereas that of the granitic rocks is due to radioactive accessory minerals.

Report discussing a study in which a suite of 50 rock specimens collected by the 1947 Washburn Mount McKinley Expedition was scanned radiometrically.