By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Located in the northwest corner of Nevada, Washoe County does not have the basin-and-range topography so characteristic of most of Nevada. Instead, it contains a series of valleys - former lakes - separated by low divides. Many lakes still fill the valleys in the northern part of the county, and Pyramid and Winnemucca Lakes in the central part are the largest natural bodies of water in the State. The Virginia Mountains extend northwestward across the central part of the county. South of Reno, the Sierra Nevada is the dominant feature of the western part of the county.
The northern part of the county is underlain by lavas, tuffs, and lake beds that, for the most part, contain no economic mineral deposits, but several mining districts in the southern part of the county have produced considerable amounts of gold and silver (Overton, 1947, p. 46-47). Prominent among these are Olinghouse, Leadville, Wedekind and Pyramid. Considerable placer mining was done in the early days at Little Valley, Peavine, and Olinghouse, but there are no reliable production data on these operations (Vanderburg, 1936a, p. 163-166).
The prospectors who flooded into Comstock soon overflowed into adjacent southern Washoe County and discovered mineral deposits in the Jumbo, Galena, and Peavine districts.
Production of gold in the county from 1902 through 1959 was 46,107 ounces.
Although small amounts of gold have been produced from most of the districts in the county, only the Olinghouse may be considered primarily a gold district; it alone has produced more than 10,000 ounces.
The Olinghouse (White Horse) district is in southeast Washoe County (lat 39Â°40' N., long 119Â°25' E.), about 12 miles south of Pyramid Lake.
The district was prospected first in 1860, but very little work was done until 1901-3, the period of greatest activity (Hill, 1910a, p. 103). In the mid-1930's there was a brief revival of activity; during the 1940's and 1950's there was only small-scale production by lessees (Overton, 1947, p. 71-72). Production from 1902 through 1921 was $509,530 (about 24,700 ounces) in gold (Lincoln, 1923, p. 240). Total gold production through 1959 was about 36,000 ounces.
The dominant country rock is an older andesite of Tertiary age (Hill, 1910a, p. 104-105) intruded by dikes and sills of porphyritic rhyolite and later andeÂ¬site. The ore deposits are in the older andesite and consist of zones of altered country rock adjacent to the intrusives. The ore minerals are free gold and small amounts of silver chloride. Minor amounts of chalcopyrite, pyrite, calcite, and quartz are present (Overton, 1947, p. 71).
Vanderburg (1936a, p. 164-166) reported some small-scale placer mining in this district throughout its history, but he gave no production data.