Abstract: Ten days were spent during June 1955, examining the sedimentary rocks along the San Juan and Colorado Rivers between Mexican Hat, Utah, and Lee's Ferry, Arizona. The most favorable area for uranium deposits occurs in the Shinarump member of the Chinle formation between Clay Hills Crossing and Spencer Camp along the San Juan River. Mineralization is spotty and deposits are small and almost all below ore-grade. Only one small mine, the Whirlwind, is currently producing ore. Gray-green alteration of the underlying Moenkopi is moderately developed in the vicinity of the Whirlwind mine; elsewhere alteration is weakly developed.