During recent years there has been a strong demand for molybdenum ore, and many articles descriptive of deposits of molybdenite (sulphide of molybdenum) have been published. Little has been printed, however, about the deposits of wulfenite (molybdate of lead) that occur in numerous places in the Southwest. The Arizona Bureau of Mines considers itself fortunate, therefore, in being able to publish this description of the most productive wulfenite deposit in Arizona. The author's suggestion that wulfenite may be a primary mineral that has been deposited in the oxidized zone by ascending solutions will doubtless be criticised by geologists who are unfamiliar with deposits of this mineral, but it is the only theory yet offered that appears to conform to observed facts. 10 p.