Cambrian Prospect Mountain Quartzite and seven underlying units, tentatively considered Precambrian, are mapped in the Beaver Mountains. Assigned to the Precambrian is 5,145 feet of slate, argillite, marble, metasiltstone, quartzite, and conglomerate, which have undergone very low-grade regional metamorphism. The uppermost Precambrian unit, a purple conglomeratic quartzite, is correlated with the Mutual Formation of north-central Utah. The overlying tan and pink Prospect Mountain Quartzite is at least 4,000 feet thick. Correlation of the Beaver Mountains section with strata from the Canyon Range, central Utah, is established. Tentative correlations, with late Precambrian McCoy Creek Group of eastern Nevada and western Utah are suggested.