Loss of uranium from crystallized silicic volcanic rocks

Dense primarily crystallized silicic groundmass material from two welded ash-flow units and one lava flow of Tertiary age from the Western United States contain only 20 to 60 percent of the uranium present in nonhydrated glass from the rock units. These differences reflect loss of uranium from the crystallized specimens, probably as a result of groundwater leaching. It appears likely that most crystallized silicic volcanic rocks have lost comparable amounts of uranium.