By A. H. KOSCHMANN and M. H. BERGENDAHL - USGS 1968
Mining began in Humboldt County in the early 1860's and for many years there was sporadic production from several districts. The discovery of fabulously rich gold ores in the National district in 1907 probably was the most significant event in the mining history of the county. These rich ores were soon depleted, and mining activity declined until 1935, when it increased with the discovery of ore in the Jumbo mine in the Awakening district.
The Getchell mine, in the Potosi district, became active in 1938, and for several years thereafter it was the largest gold producer in the State. Most of the gold mined in Humboldt County has come from lodes, but there has also been considerable placer gold produced from the Dutch Flat district.
Vanderburg (1938b, p. 13, 14) listed production data for gold as early as 1890 and for silver and gold as early as 1870. For the period 1870-90, a total of $4,975,372 in gold and silver was produced. From 1890 through 1903 about 31,830 ounces of lode and placer gold was mined. From 1905 through 1959, a total of 811,712 ounces of lode gold and 36,720 ounces of placer gold was produced.
Humboldt County contains several north-trending mountain ranges, separated by arid undrained valleys, many of which contain playa lakes.
The Awakening district is about 45 miles northwest of Winnemucca in the Slumbering Hills.
About 1910 mining began in this area, and there was a small production of gold and silver from 1912 to 1918. In 1935 the discovery of the Jumbo mine opened a new period of large-scale activity. The early production could not be determined, but from 1935 through 1959, a total of 25,648 ounces of gold was produced.
Metamorphosed muds and impure sandstones, now slates and schists of probable Mesozoic age, are exposed throughout most of the area (Calkins, 1938, p. 9-15). A body of quartz monzonite has intruded the Mesozoic rocks and produced zones of contact metamorphism. Aplite and pegmatite dikes are associated with the intrusive. Tertiary latite and andesite flows, underlain by lake beds, cap the higher parts of the area.
Most ore deposits are gold-bearing quartz veins in the slates (Calkins, 1938, p. 15-22). Most of the veins are less than 1 foot thick and have numerous branches. Their average strike is north and their dips are variable. The Jumbo deposit, however, is completely different from the other veins of the district. Its most characteristic feature is the abundant adularia and sparse quartz in the gangue. The veins are small and irregularly distributed, as in a stockwork (Calkins, 1938, p. 19-20).
DUTCH FLAT DISTRICT
The Dutch Flat placer district, 18 miles northeast of Winnemucca and 18 miles north of Golconda, was discovered in 1893 and produced about $75,000 in gold the first year (Vanderburg, 1936a, p. 94). Total gold production through 1959 was about 10,000 ounces.
The deposits are stream and slope-wash gravels in an area 11/2 miles long and 300 to 2,000 feet wide (Willden and Hotz, 1955, p. 666). In addition to gold, significant quantities of scheelite and cinnabar occur in the placers. The ore minerals come from low-grade lode deposits in a granodiorite stock and in folded early Paleozoic sedimentary rocks.
The lode deposits are of two types: gold-quartz veins that contain some sulfides and a little scheelite, and disseminated cinnabar in a shear zone that cuts metamorphosed shale and feldspathic quartzite (Willden and Hotz, 1955, p. 665).
GOLD RUN DISTRICT
Located in southeast Humboldt County, 12 miles south of Golconda, the Gold Run (Adelaide) district was organized in 1866. Gold has been a byproduct of ores mined for copper and silver. Placer gold was mined sporadically along Gold Run Creek, and total production from this source was about 2,000 ounces. Production of byproduct gold from 1907 through 1959 was 23,747 ounces.
At the Adelaide mine, the principal mine of the district (Vanderburg, 1938b, p. 24), the ore occurs as replacements of limestone beds and consists of chalcopyrite, pyrrhotite, sphalerite, and galena in a gangue of calcite, garnet, vesuvianite. Some specimens contained a little scheelite.
The National district is in northeastern Humboldt County on the west slope of the Santa Rosa Range, 18 miles southeast of McDermitt.
Although the Santa Rosa Range had been prospected with minor success since the 1860's, it was not until 1907 that the rich deposits at National were discovered. The unusually high grade ore body at the National soon made it the leading mine in the district. Some of the ore was valued at $30 per pound. As may be expected, this attracted many individuals of questionable character, and the history of the camp is marked by numerous incidents of violence and disorder and a trial that attracted wide attention (Lindgren, 1915, p. 19, 20, 52-54).
Production of the district from 1909 through 1959 was 177,000 ounces, all from lode deposits.
The northern part of the Santa Rosa Range is composed predominantly of basaltic lava flows of probable Miocene age (Lindgren, 1915, p. 21-22). At National mine, basaltic tuffs and lacustrine beds are overlain by latite, basaltic flows, and a rhyolite flow. Necks and dikes of this rhyolite cut all the older rocks. Locally basalt flows cover the rhyolite. The rocks dip 8° to 15° NE.
The ore deposits are in fissure veins that have a northward trend and steep east or west dips. The veins cut the youngest rocks in the district and are therefore believed to be Miocene or post-Miocene in age (Lindgren, 1915, p. 32). Most of the veins are rich in silver; ruby silver is the chief ore mineral. The National ore shoot is an exception. Here the ore mineral is coarse electrum irregularly distributed near the footwall of the quartz vein (Lindgren, 1915, p. 31, 32).
Stibnite is the characteristic mineral of all the veins. Other sulfides present are pyrite, calcopyrite, arsenopyrite, sphalerite, and galena in a gangue of banded and vuggy quartz.
PARADISE VALLEY DISTRICT
Located on the east slope of the Santa Rosa Range, 11 miles northwest of the town of Paradise Valley, the Paradise Valley district was discovered in 1868. During 1879-91 the mines reached their peak production; then, operations ceased abruptly. Brief revivals took place in 1907-15 and 1931-35 (Vanderburg, 1938b, p. 38). From 1947 through 1959, only 10 ounces of gold was reported.
Silver is the chief commodity mined in this district; gold is a byproduct. Some placer gold was produced in 1909-15. Total gold production through 1959 was about 70,000 ounces.
The ore deposits are quartz veins in shale, calcareous slate, and porphyry. The veins, which strike north and dip steeply east, contain cerargyrite, chalcopyrite, pyrargyrite, sphalerite, and pyrite, in a gangue of quartz (Vanderburg, 1938b, p. 38-40).
The Potosi district is in T. 38 and 39 N., R. 42 E., in the northern Osgood Mountains.
Gold mining in the district was insignificant until the discovery of the Getchell ore body in 1934. Large-scale open-cut mining of the Getchell began in 1938, and during 1939-41 it was the leading gold-producer in the State. The mine was permitted to remain open during World War II in order to produce tungsten and arsenic which were in short supply. A scarcity of labor and materials forced the mine to close in 1945.
Large-scale mining of gold was resumed in 1948 and continued through 1950, when attention was diverted to mining of tungsten ores. During 1952-57 the Getchell and Riley mines were the major tungsten producers in Nevada. Exploration and development of gold properties in the Getchell mine area during 1959-61 were successful, and gold mining was resumed in 1962.
Published data are incomplete and show gold production of only 116,015 ounces. Total gold production is probably worth about $17 million or roughly 485,700 ounces (R. L. Erickson, oral commun., 1963).
The geology of the district is fairly complex. The eastern part is underlain by shale, slate, and limestone of the Preble Formation of Cambrian age and by limestone, shale, and conglomerate of Pennsyl-vanian and Permian age. The higher central part of the district is occupied by a stock of granodiorite of Cretaceous age.
Overlying the granodiorite in the north-central part of the district is a thrust plate of phyllite, calc-silicate rock, marble, and recrystal-lized chert, representing part of the Comus Formation of Ordovician age. North-trending normal faults dislocated the rocks after the period of thrust faulting (Hotz and Willden, 1961).
The major ore deposits, which are along the north-trending Getchell fault, are sheetlike masses that are distributed irregularly in veins along various fault branches near the surface but that coalesce at depth along the main fault. The veins consist of sheared and mineralized sedimentary rock which is cut by quartz and calcite veinlets and which contains a soft carbonaceous gumbo. Most of the gold is in the gumbo.
Gangue, in addition to gumbo, consists of small amounts of barite, chabazite, gypsum, and fluorite. Pyrite, pyrrhotite, arsenopyrite, marcasite, orpiment, realgar, stibnite, ilsemannite, cinnabar, magnetite, gold, and scheelite are the major ore minerals.
Gold occurs as minute particles associated with magnetite and carbonaceous material in the gumbo and also as submicroscopic particles in pyrite and marcasite. The richer gold accumulations are characterized by abundant realgar (Joralemon, 1951, p. 270-282).
R. L. Erickson (oral commun., 1963) noted a relationship of arsenic, mercury, and tungsten in geochemical anomalies in the district and suggested that these anomalies are worthy of exploration for gold.
WARM SPRINGS DISTRICT
The Warm Springs district is in northwest Humboldt County near Denio, Oreg. The first discoveries were in 1863, but production was hindered for some time by the hostile Bannock Indians, who burned a mill and drove out the miners (Vanderburg, 1938b, p. 49). The principal mine in the district is the Ashdown.
Production of the district is not known, but Vanderburg (1938b, p. 49) estimated that it was $400,000, mostly in gold from the Ashdown mine. From 1937 through 1957, a total of 5,178 ounces of lode gold and 10 ounces of placer gold was reported. Total gold production through 1959 was about 24,000 ounces.
The country rock is slate of undetermined age and is intruded by granite and porphyry. At the Ashdown mine the ore deposit is in a quartz vein in granite. Free gold occurs in a gangue of quartz.
The first discovery in this district, which is 4 miles northwest of the town of Winnemucca, was made in 1863 by an Indian named Winnemucca (Vanderburg, 1938a, p. 51-54). The most important mine in the early days was the Pride of the Mountain, which produced an estimated $1 million in precious metals (Ferguson and others, 1951). In the early 1900's, high-grade gold ore discoveries near Barrett Springs created a short-lived rush; from 1937 through 1943 there was a renewal of activity, mainly at the Pansy Lee mine.
Production data are incomplete for the early years. During 1910-35, a total of $132,433 in gold and silver was produced (Vanderburg, 1938a, p. 51), and during 1935-59, about 10,070 ounces of gold was produced. Total gold production through 1959, including early production from the Pride of the Mountain mine, was probably 35,000 ounces.
The deposits on Winnemucca Mountain include veins and replacement deposits in hornfels and limestone of the Winnemucca Formation, of Late Triassic age. This formation locally is intruded by diorite (Ferguson and others, 1951). In the Barrett Springs area, the deposits are gold and silver-rich quartz stringers and veins in the slates of the Raspberry Formation of Late Triassic age (Ferguson and others, 1951).