Named for exposures on Duffer Peak. Type locality designated as Duffer Peak, Pine Forest Range in northwest part of Duffer Peak 15' quad, Humboldt Co, NV. Reference localities are slopes surrounding Onion Valley Reservoir and underlying Corral Meadow in Duffer Peak 15' quad and in immediate vicinities of Little Onion Reservoir and Hollywood Meadow in Idaho Canyon 15' quad. Texture varies from medium-grained equigranular to inequigranular porphyritic. Intrudes Triassic(?) quartzite, marble, and amphibolite and Permian or older Happy Creek Volcanic Series. Intruded by Cretaceous alaskite and aplite. Unconformably underlies Tertiary volcanic units. K-Ar age is 96.2 +/-3.5 Ma (E.H. McKee). Shown on geologic map of Duffer Peak 15' quad and cross section as of Late Cretaceous age.

Source: GNU records (USGS DDS-6; Menlo GNULEX).