The Edna Mountain Formation was named by Ferguson and others (1952) from exposure at Edna Mountain in the Golconda Quadrangle, 30 miles northwest of the town of Battle Mountain. The exposure along Cottonwood Creek, at the north end of Battle Mountain, is the only occurrence of the Edna Mountain in the evaluation area.

Brachiopods found within the Edna Mountain Formation are Late Permian (Guadalupian) age. The Edna Mountain is time equivalent with the Phosphoria Formation and the upper portion of the Park City Group in the eastern portion of the evaluation area.

At the type section, the Edna Mountain Formation is a sequence of interbedded, calcareous, greenish or brownish-gray shale, bluish-grey limestone, brown sandstone, and chert-pebble conglomerate in beds up to 20 feet in thickness. The conglomerates contain angular to subrounded black, grey, brown, and green chert granules and pebbles (Roberts, 1964b). The Edna Mountain Formation rests disconformably upon the Antler Peak Limestone and is thrust over by the Pumpernickle Formation.

In Elko County, the Edna Mountain Formation has been described in several sections where it unconformably overlies or is in thrust contact with western assemblage rocks and is considered allochthonous (Coats, 1985). In the Divide Peak area east of the Independence Mountains, the Edna Mountain is composed of chert-quartz conglomerate, brown weathering quartz arenite which grades into granule conglomerate, and purplish-red to brown weathering siltstone (Coats and Gordon, 1972).

Small patches of Edna Mountain are also present in the Tuscarora Range within the Tuscarora Quadrangle, where it is composed of coarse-grained arenite and conglomerate which unconformably overlie western assemblage rocks (Coats, 1985).

In the California Mountain Quadrangle along the eastern flank of the Independence Mountains, the Edna Mountain is composed of conglomerate. In the Beaver Peak Quadrangle in the Tuscarora Mountains it is composed of greenish quartz-chert conglomerate and interbedded coarse-grained arenite (Coats, 1985).

In the Hubbard Basin Quadrangle at the northern tip of the Snake Mountains, the Edna Mountain is a tan weathering siltstone which has a thrusted lower contact (Coats, 1985). In the Snake Mountains, Peterson (1968) mapped about 2,000 feet of thin-bedded, yellow-brown weathering sandstone with subangular to subrounded clasts of chert, quartzite, and limestone, and fossil molds of bryozoa and brachiopods. These rocks were questionably assigned to the Edna Mountain Formation by Coats (1985).

The thickness of the Edna Mountain Formation is estimated at 200 to 250 feet at the type section, however the section is highly faulted (Roberts, 1964b). At Double Mountain it is also highly faulted and may be about 250 feet thick (Coats and Gordon, 1972). It is about 250 feet in the western Tuscarora Mountains within the Tuscarora Quadrangle (Coats, 1985), and is about 2,000 feet thick in the Snake Mountains (Peterson, 1968; Coats, 1985).

The Edna Mountain Formation is exposed in the Battle Mountain area, at Divide Peak east of the Independence Mountains, in the California Quadrangle of the Independence Mountains, the Beaver Peak Quadrangle on the eastern flank of the Tuscarora Mountains, along the western margin of the Tuscarora Mountains, the Hubbard Basin Quadrangle just north of the Snake Mountains, and in the Snake Mountains.

The depositional setting of the Edna Mountain Formation is very poorly understood. Brachiopods, mollusks and bryozoa suggest that these siltstones, sandstones, conglomerates, and limestones are shallow marine in origin. A deltaic environment is plausible for the Edna Mountain.