The Aura Formation was named for the Aura mining district on the east slope of the Bull Run Mountains, in T. 44 N., R. 52 E., in the northern portion of the Bull Run Quadrangle (Decker, 1962).

No fossils have been recovered from the Aura Formation (Decker, 1962; Coats, 1985). It was assigned an Ordovician age by Decker (1962) based upon its stratigraphic position between the Chellis Limestone and underlying Porter Peak Limestone. Decker (1962) suggested a correlation of part of the unit with the Eureka Quartzite.

The Aura Formation is lithologically diverse with three informal members (Decker, 1962). The lower portion of the unit consists of brown to black phyllite and chert which alternate with blue-gray limestone in laminae less than an inch up to beds 300 feet in thickness. The middle portion of the Aura is brown, medium-grained, vitreous quartzite up to 500 feet thick which has locally been cut out by faulting (Coats, 1985). The upper member of the Aura Formation is composed of brown and black laminated phyllite interbedded with thin calcareous layers (Decker, 1962).

The thickness of the Aura is estimated at 3,800 feet based upon several faulted sections (Decker, 1962).

The Aura Formation has been mapped in the Bull Run Quadrangle in northern Elko County (Decker, 1962).

The depositional setting for the Aura Formation is very poorly understood as a result of its local, highly faulted, non-fossiliferous, and metamorphosed exposures. The Aura probably represents deposition along the Ordovician outer shelf and upper slope.