By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
In 1910 this county was created from what was formerly the north part of Esmeralda County. Typical of the Great Basin, Mineral County contains narrow, elongate mountain ranges separated by valleys having interior drainage. Most of the mountain ranges are mineralized; the principal ranges are the Wassuk, Gabbs Valley, Gillis, Pilot, and Excelsior. A great variety of mineral products has been mined in this county; gold has been the most valuable product, but considerable amounts of silver, lead, zinc, copper, tungsten, and mercury have been mined.
Production data for the county go back only to 1910, when the county was founded. Vanderburg (1937b, p. 10) listed 219,435 ounces of lode gold and 1,963 ounces of placer gold for 1910-34. From 1935 through 1959 production was 43,986 ounces of lode gold and 738 ounces of placer gold. Total gold production for Mineral County from 1910 through 1959 was 266,122 ounces.
The Aurora district is in western Mineral County, 3 miles east of the Nevada-California State line and 30 miles southwest of Hawthorne.
Gold-silver veins were discovered here in 1860. Almost immediately a town named Esmeralda was built, but less than a year later it was abandoned in favor of a site XXX miles north that is the present location of the town of Aurora, which by 1864 had a population of about 10,000 (Hill, 1915, p. 141). Despite litigation over claims and uncertainty about the location of the California-Nevada boundary, the district prospered until the mid-1880's when the high-grade ore was depleted. In the 1930's there was only small-scale mining by lessees, and the town of Aurora, though substantially built, was almost in ruins (Vanderburg, 1937b, p. 14).
Data for production in the early days are incomplete. Hill (1915, p. 142) estimated at least $27 million in gold and silver from 1861 to 1869. For the same period, Vanderburg (1937b, p. 14, 15) estimated at least $30 million in precious metals. From 1910 to 1920 the district produced $1,882,861 (about 91,400 ounces) in gold; the total through 1959 was about 93,600 ounces.
The following account of the geology is condensed from Hill (1915, p. 143-150). Nearly all the rocks exposed in the area are of volcanic origin and consist, from oldest to youngest, of biotite-quartz latite, andesite, rhyolite, and basalt. After each of the periods of extrusion of andesite, rhyolite, and basalt were periods of erosion. The oldest flow was extruded on a granitic basement rock.
The ore deposits are in veins that cut the biotite-quartz latite and andesite. Most of the veins strike about N. 45Â° E. and dip moderately southeast. Most of the veins are IV2 to 4 feet thick, but some are as much as 80 feet thick. The veins send off numerous branches which become, in many places, an interlacing network of veinlets. Fine-grained quartz that is usually banded makes up the bulk of the veins; small cavities lined with tiny quartz crystals are common. The ore consists of quartz, adularia, argentiferous tetrahedrite, pyrite, chalcopyrite, and a soft blue-gray material containing gold and possibly silver with selenium. Free gold is present in the richest ores. The occurrence of selenium without tellurium in these ores is unusual and has been noted in only a few mining camps.
Page 1 of 4