The Havallah Formation was named for exposures near Hoffman Canyon in the Tobin Range, formerly known as the Havallah Range, 28 miles west-southwest of the town of Battle Mountain (Muller and others, 1951).

Fusulinids from the lower member of the Havallah Formation are of Middle Pennsylvanian (Atokan) age but are contained in rounded detrital grains that may be reworked (Roberts, 1964). No fossils have been recovered from the middle member. Fusulinids from the upper member at Battle Mountain give an Early Permian (late Wolfcampian to early Leonardian) age. Conodonts collected in the Shoshone Range suggest a Middle or Late Pennsylvanian (Des Moinian to middle Virgillian) age (Stewart and McKee, 1977).

At Battle Mountain, Roberts (1964b) described 4,500 feet of Havallah Formation that he divided into three members with contacts that may in part represent erosional unconformities. The lower Jory Member is composed of pebbly sandstone with minor interbeds of conglomerate, shale and chert about 1,180 feet in thickness. The sandstones are brown and coarse-grained, with subrounded to well-rounded grains of quartz, quartzite and chert, and minor orthoclase, plagioclase, microcline, biotite, collophane (apatite) and muscovite. Sole markings are present on the base of some sandstone and conglomerate beds (Roberts, 1964b).

The middle Trenton Canyon Member is composed of thin-bedded red, green, purple and gray chert commonly in layers 4 inches in thickness, interbedded with thin reddish to orange shale partings and beds up to 6 inches thick (Roberts, 1964b). The Trenton Member has an estimated thickness of 1,000 feet and is locally hornfelsed.

The upper Mill Canyon Member at Battle Mountain is composed of about 2,386 feet of quartzite, sandy limestone, shale and chert (Roberts, 1964b). The medium to dark gray quartzites occur both as medium-bedded, evenly and thinly laminated quartzite in layers from a few inches up to 2 feet in thickness, and as massive, thick-bedded quartzite (Roberts, 1964b). Much of the quartzite is calcareous and grades laterally into limey sandstone and dark gray limestones from a few inches to 50 feet in thickness. The limestones are clastic and contain abundant bioclastic material. Along strike, the limestones both interfinger with, and grade into grey to brown calcareous shale. Local conglomerates contain chert, quartzite, and limestone pebbles up to 4 inches across in a sandy calcareous matrix (Roberts, 1964b). Worm and various invertebrate tracks are locally abundant within the Mill Canyon Member.

In the Toiyabe Range, the Havallah Formation is composed of greenish-gray, yellowish-gray, and yellow-brown siltstone and shale, yelllow-brown, very fine-grained sandstone, with minor conglomerate and chert. Invertebrate tracks are abundant within these sediments (Stewart and McKee, 1977).

In the Mount Lewis area of the Shoshone Range, a few small outcrops of Havallah with vertical bedding and a thickness of perhaps 1,000 feet have been described by Gilluly and Gates (1965). These outcrops consist of dark brown, calcareous mudstone or argillite that contains carbonaceous corkscrew shaped markings termed "feathery algae" and worm tracks (Gilluly and Gates, 1965).

In the Burner Hills area in northern Elko County, an early Pennsylvanian sedimentary sequence of unknown thickness has been correlated with the Havallah Formation (Coats, 1985). The rocks are composed of dark gray, poorly sorted, feldspathic and chert-rich sandstone, and minor greenstone and interbedded gray limestone lenses. In the Owyhee Quadrangle, the Slate of Sikikareh Mountain (Coats, 1971), although of uncertain age, has been correlated with the Havallah (Coats, 1985). The Slate of Sikikareh Mountainis composed of black argillaceous and green chloritic slate that has been locally metamorphosed to an andalusite-bearing hornfels (Coats, 1971).

The Havallah Formation is about 4,500 feet thick at Battle Mountain (Roberts, 1964b) and about 1,000 feet in the Shoshone Range (Stewart and McKee, 1977). Ferguson and others (1952) estimated the total thickness of the Havallah in western Lander County to be 10,000 feet.

The Havallah Formation is exposed at Battle Mountain, in the Shoshone and Toiyabe Ranges, and areas to the west of the evaluation area with possible equivalents in northern Elko County in the Burner Hills and Owyhee Quadrangles.

The Havallah Formation represents tectonically interleaved marine sediments that form the upper plate of the Golconda allochthon. Most workers suggest a deep-water environment for these rocks, with initial deposition in a subduction complex on the sea floor. This is based on sole markings such as flute casts present at the base of coarse grained and pebbly sandstones and conglomerates which suggest density current or grain flow deposition, convolute bedding in silty limestones, the abundance of radiolarian chert, and preservation of deep-water trace fossils as invertebrate tracks in limestones and sandstones in the upper member of the formation (Stewart and others, 1977). Roberts (1964b) has suggested that the Havallah Formation shallows upwards and that much of the chert is formed by spicules of sponges that lived in water depths of less than 300 feet. The presence of phosphatic minerals in the sandstones such as collophane also suggests relatively shallow water.