Black Mesa, located in northeastern Arizona, is a southwest-dipping cuesta, nearly circular in plan, with a diameter of approximately 60 miles (Figure 1). The mesa is capped with sedimentary rocks of the Upper Cretaceous Mesaverde Group. During the 1954 to 1968 period, 16,779.90 tons of ore grading 0.17% U308 and containing 55,739.44 pounds uranium oxide (U308) were produced from 13 properties in the Toreva Formation. With the exception of two properties near Yale Point, all production came from properties located on both sides of the upper drainage of Polacca Wash in Apache County, Arizona (Figure 2).