By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Elko County is in the northeastern part of the State, and most of its gold production has come from districts in the northern and western parts of the county. Lode mines in the Jarbidge and Tuscarora districts have been the principal source of the gold, but in the early days considerable amounts of placer gold were mined at Tuscarora, Aura, Charleston, Gold Basin, Island Mountain, and Mountain City. Lesser amounts of lode and byproduct gold came from Gold Circle, Mountain City, Aura, and Edgemont.
The production of the county from 1903 through 1959 was 561,187 ounces - 554,737 ounces from lodes and 6,450 ounces from placers. Before 1903 there was considerable production, primarily from Tuscarora and Edgemont, but no complete record could be found. From 1879 through 1896, the county produced $1,017,051 in lode gold (Nolan, 1936a, p. 13). In addition, the Tuscarora district produced about $700,000 in placer gold (Nolan, 1936a, p. 14). Total gold production through 1959 was about 614,000 ounces.
The Edgemont district is in northern Elko County, on the west slope of the Centennial Range, about 10 miles north of Deep Creek.
Before about 1907 the Lucky Girl and Bull Run mines yielded about $1 million in gold (Emmons, 1910, p. 75). From 1907 through 1959 the district was dormant, producing only 4 ounces in 1950 and 74 ounces in 1951.
The deposits consist of fissure veins in contorted and fractured quartzite. Gold is associated with pyrite, galena, and pyrrhotite (Emmons, 1910, p. 75-76).
GOLD CIRCLE DISTRICT
The Gold Circle district is 45 miles north of Battle Mountain, 50 miles northeast of Golconda, and 35 miles west of Tuscarora.
Gold was discovered in 1907, and a brief boom followed. This has been a gold-silver district; a total of 109,765 ounces of lode gold and 45 ounces of placer gold was produced from 1908 to 1958, mostly from the Elko Prince mine.
The country rocks - from oldest to youngest - consist of rhyolite, andesite, and postandesite rhyolite flows and tuff (Rott, 1931, p. 10). The rocks were faulted and then mineralized. Most of the veins follow northwest-trending shear zones in the older rhyolite and the fractured contact between rhyolite and andesite.
Vein material is principally silicified breccia and minor calcite and adularia. The dominant minerals are pyrite, stromeyerite, and native gold. Minor constituents are tetrahedrite, proustite, chalcopyrite, and sphalerite.
The Jarbidge district is in northern Elko County about 60 miles west of the Utah State line and 5 miles south of the Idaho State line.
Gold ore was first discovered in 1904 (Schrader, 1912, p. 15), but the major discovery was not until 1909. A rush to the area took place the following year, and the town of Jarbidge was soon founded.
Production totaled about 217,800 ounces from 1911 through 1959.
The Jarbidge Mountains, of which the mining district is a small part, separate two major physiographic provinces: the Snake River Plain to the north and the Great Basin to the south.
The district is underlain by Tertiary volcanic rocks that were extruded on an eroded surface of Paleozoic rocks that had been intruded by granitic stocks and dikes (Schrader, 1923, p. 12-35). The Paleozoic sedimentary rocks consist of quartzite, limestone, and shale and have been considerably folded. The intrusive rock is a gray coarsely crystalline hornblende-biotite granodiorite of probable Cretaceous age. The Tertiary volcanic rocks, mostly rhyolites, are divided into two series separated by an erosion surface.
The ore deposits are gold-bearing fissure veins in the older rhyolites. These veins range from 1 to 30 feet in width and from several hundred feet to several miles in length. They are grouped into a west and east system. In the west system the veins are the more valuable; they strike north-northwestward and dip steeply eastward. In the east system the veins are narrow but persistent; they strike northward and are exposed in rocks nearer the crest of the range.
The economic metals of the district are gold and silver, and they occur as native gold, electrum, argentite, cerargyrite, and naumannite (Schrader, 1923, p. 26). Pyrite is also present. The gangue consists chiefly of quartz and adularia. Other minerals present in minor amounts are apatite, barite, calcite, chalcedony, chlorite, epidote, fluorite, hematite, hyalite, kaolin, halloysite, leverrierite, limonite, psilomelane, pyrolusite, marcasite, opaline silica, sericite, and talc.
The Tuscarora district is 45 miles northwest of Elko, near the headwaters of the South Fork of the Owyhee River.
Gold was discovered in the area in 1867 in stream gravels (Browne, 1868, p. 429-430), and outcrops of auriferous vein material were found soon afterward. During the following 9 years placers were mined, but there was no intense activity until 1876 when high-grade ore was found in the Grand Prize mine (Nolan, 1936a, p. 7-9). The usual boom period followed, accompanied by mismanagement, waste, litigations, and profiteering, so typical of the histories of mining camps throughout the West.
By 1886 the bonanza ores were exhausted, but new discoveries to the north and west created another boom, though of lesser proportions. A third revival was created by the mining of low-grade gold ores from the Dexter mine (Nolan, 1936a, p. 9), and most of the production of the district from 1895 to 1912 was from this mine. In recent years the district declined steadily with no production reported from 1955 through 1959.
Nolan (1936a, p. 10-14) in reviewing the production history of the district noted that estimates of production before 1902 varied widely, but that a reasonable compromise would be about $10 million in gold and silver. From 1902 through 1959, a total of 15,662 ounces of gold was mined, most of it from lodes. The placer gold production of the district, most of it mined in the early days, amounted to about $700,000 (Nolan, 1936a, p. 14). Total gold production of the district through 1959 probably was at least 100,000 ounces.
The bedrock of the area consists of bedded volcanic breccias and tuffs about 5,000 feet thick and dark-green andesite porphyry that is intrusive into the pyroclastics (Nolan, 1936a, p. 14-35). The bedded rocks have been tilted to the east and southeast. The rocks are also faulted, but the nature and extent of faulting are not clear.
There are three types of deposits: (1) silver lodes rich in native silver and silver halides, argentite, stephanite, proustite, pyrargyrite, pyrite, enargite, arsenopyrite, bornite, chalcopyrite, sphalerite, and galena with quartz and calcite gangue, in the andesite masses; (2) gold deposits consisting of quartz and adularia fissure fillings and zones of quartz stringers in the bedded pyroclastics; and (3) gold placers.