The Johns Wash Limestone was named by Drewes and Palmer (1957) for limestones at the head of Johns Wash in T. 11 N., R. 68 E., in the southern portion of the Snake Range.

Fossils are sparse in the Johns Wash Limestone. Trilobite fragments indicate an early or middle Late Cambrian age (Drewes and Palmer, 1957). The Johns Wash Limestone conformably underlies and overlies the Lincoln Peak Formation and Corset Springs Shale respectively. Fossils found in the Johns Wash Formation resemble those found near the base of the Dunderberg Shale in the Eureka District (Kellogg, 1963).

At its type section in the Snake Range, the base of the Johns Wash Limestone is a thick bed of edgewise limestone-pebble conglomerate (Drewes and Palmer, 1957). Overlying the conglomerate are light to dark gray, coarse-grained limestones which show cross-bedding and wavy bedding. The limestones are bioclastic in the upper portion of the unit with fragments of trilobites and pelmatazoans that are often unidentifiable (Drewes and Palmer, 1957). Ooids and pisolites are also characteristic of the limestones which in places show alternation of light and dark bands accentuating cross-bedding (Hose and Blake, 1976).

In the Pilot Range, the Johns Wash conformably overlies the Dunderberg Shale. It is composed of a lower 250 feet of shale argillite and phyllite, and an upper 700 feet of gray massive dolomite (O'Neill, 1968).

The Johns Wash Limestone is about 250 feet thick at its type section in the southern Snake Range (Drewes and Palmer, 1957), and 950 feet thick in the Pilot Range (O'Neill, 1968).

The Johns Wash Limestone has only been recognized as a mappable unit in the southern portion of the Snake and Pilot Ranges. Hose and Blake (1976) speculate that it may be present in the southern Schell Creek and Egan Ranges as units such as the Emigrant Springs Limestone of Kellogg (1963).

The bioclastic, oolitic, pelmatazoan-bearing limestones and limestone pebble conglomerates, abundant in the upper 150 feet of the underlying Lincoln Peak Formation and at the base of the Johns Wash Limestone, suggest shallow marine shelf deposition.