Rochester District
Overview
Other Names: Sacramento, Nenzel, Oreana
County: Pershing
Discovered: 1860s (1912)
Commodities: silver, gold, lead, copper, zinc, antimony, tungsten, dumortierite, andalusite
Comments
Located in Rochester Canyon in the southern part of the Humboldt Range. The original Sacramento district included the later Rochester district; the Rochester Mine was one of the first mines in the historic Sacramento district. The Rochester name was applied to the southern part of Sacramento district following silver discoveries in 1912 by J. Nenzel (Shamberger, 1973b). The western part of district was included in the Oreana district of Lotz (1934).
References
General Land Office, 1866; Raymond, 1868, p. 125; Raymond, 1870, p. 137, 192; Lincoln, 1923, p. 213; Stoddard, 1932, p. 79; Lotz, 1934, p. 23; Vanderburg, 1936b, p. 28; Shamberger, 1973b, p. 2; Schilling, 1976; Johnson, 1977, p. 78; Vikre, 1981, p. 37; Stager and Tingley, 1988, p. 188
Rochester Placer District Description
Location
West flank of the Humboldt Range, Tps. 28 and 29 N., Rs. 33 and 34 E.
Topographic Maps
Unionville 15-minute quadrangle; Rochester mining district, special map, scale 1 : 24,000.
Geologic Maps
Wallace, Tatlock, Silberling, and Irwin, 1969, Geologic map of the Unionville quadrangle, Pershing County, Nevada, scale 1:62,500.
Access
From Lovelock, 13 miles north on Interstate 80 to Oreana and junction with State Highway 50; from there, it is about 8 miles east to placer areas north and south of Rochester.
Extent
Placers were worked in Sacramento, Limerick, Rochester, and Weaver Canyons on the west flank of the Humboldt Range. The placers were discovered in the early 1860's about the same time as the lode mines and worked on a small scale. Early placer activity was apparently concentrated in Rochester Canyon, but the placer workings are now covered by mill tailings from the lode mines.
The gravels in Rochester Canyon below lower Rochester (sees. 13 and 14, T. 28 N., R. 33 E.) are 50 to several hundred feet thick and contain gold throughout the deposit. Gold is also reported in Tertiary gravels (sec. 23, T. 28 N., R. 33 E.) northwest of Packard Flat in the West Humboldt Range.
Placers in Limerick Canyon are the most productive in the district. Early placer miners are said to have worked the gravels in the canyon, but little information has been found about production from this location. Near the head of the canyon, west of Spring Valley Pass, an alluvial basin about 1.5 miles wide and 1 mile long (sees. 4, 5, 8, 9, T. 28 N., R. 34 E.) known as Limerick Basin was the center for most placer-mining activity in the district in the 20th century.
The gold is mainly concentrated on bedrock or in pay streaks just above bedrock; at the west end of the basin, however, gold was reported throughout the gravel thickness of 2-38 feet. Some gravel has yielded as much as $12 to $35 per cubic yard.
The placers in Sacramento Canyon (southern part of T. 29 N., Rs. 33 and 34 E.) in the north end of the Rochester district were discovered in 1912 and worked on a small scale.
Small placers were worked in Weaver Canyon (sec. 19, 20, 21, T. 28 N., R. 34 E.) in the south end of the Rochester district.
Production History
The production for the placers on the west side of the Humboldt Range (Rochester district, proper) is difficult to deter- mine, because data for both Spring Valley and Rochester districts were grouped for most years. Early production has been estimated between 4,500 and 50,000 ounces; production during the 20th century is about 3,000 ounces.
Most of the placer mining in the Rochester district was on a small scale with drywashers, but a few small placer operations were mechanized. One operation in 1936 and 1937 at the Rhyolite placers in Limerick Canyon used 5/8-cubic-yard shovels and 2.5 -cubic-yard trucks 2 to dig and transport the gravels to a stationary washing plant. Most of the work, however, was done by digging shafts to the pay streak and using drywashers to concentrate the fairly coarse gold.
Source
The Rochester district is primarily a silver mining district, but a few small lode-gold mines are found in the area. The gold is associated with quartz and tourmaline in veins that appear unrelated to the silver veins. In at least one place, placer gravels were traced to the lode source at the Hagan lode in Limerick Basin. The gold vein there contains quartz, microcline and tourmaline and cuts a quartz keratophyre phase of the Limerick Greenstone (Early Triassic). The gold veins are genetically associated with leucogranite (Early Triassic).
Literature
Bergendahl, 1964 : Placer-production estimate for Rochester district.
Gardner and Allsman, 1938: Depth of pay gravel and overburden; placer-mining techniques and operations at Rhyolite placer, Limerick Canyon.
Knopf, 1924: Brief description of history and production of placers in Limerick Basin; depth of gravel; average value; methods of mining; source.
Mining Journal, 1931: Reports sale and lease of placer ground in Rochester Canyon; price paid for land to Southern Pacific Company; thickness of gravel; average value per yard; purchase price of placer.
Southern Pacific Company, 1964: Locates placer gravels in the lower parts of Limerick and Rochester Canyons; indicates limited promise for future development.
Schrader, 1915: Describes placers in Rochester, Weaver, and Limerick Canyons. Details of depth of gravel, value, size, and production from Limerick Canyon.
Vanderburg, 1936a: Extent of placers; names of placer gulches; distribution of gold and thickness of gravels in Limerick Canyon; compares lithology of gravels in Limerick Basin with that of American Canyon. 1936b: Placer-mining operations in 1930's in Limerick Canyon; depth of gravels worked in Limerick Basin; size and fineness of gold recovered.
