Pioche Deposits

Site Name

Primary: Pioche Deposits
Secondary: Caselton (Combined Metals Reduction Co.) Mine
Secondary: Ely Valley Mine
Secondary: Prince-Virginia Louise-Davidson Mine
Secondary: Raymond and Ely Mine

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Commodity

Primary: Lead
Primary: Silver
Primary: Gold
Primary: Manganese
Secondary: Copper
Secondary: Zinc
Secondary: Iron
Tertiary: Arsenic

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Location

State: Nevada
County: Lincoln
District: Pioche District

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Land Status

Land ownership: Private
Note: the land ownership field only identifies whether the area the mine is in is generally on public lands like Forest Service or BLM land, or if it is in an area that is generally private property. It does not definitively identify property status, nor does it indicate claim status or whether an area is open to prospecting. Always respect private property.

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Kerr-McGee

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Production

Not available

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Deposit

Record Type: District
Operation Category: Past Producer
Deposit Type: fissure veins; limestone replacement
Operation Type: Underground
Year First Production: 1869
Discovery Year: 1863
Years of Production:
Organization:
Significant: Y
Deposit Size: L

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Physiography

Not available

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Mineral Deposit Model

Model Name: Polymetallic replacement

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Orebody

Form: tabular to lenticular orebodies, tapering away from fissures

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Structure

Type: R
Description: E-W and N-S normal faulting before thrusting; N60 degree S faults mineralized; N-S, NW-trending post mineral. The Pioche Hills appear to be a window in a regional thrust of upper Cambrian rocks over lower Cambrian and Tertiary volcanics. Pioche Shale bed dropped by closely spaced parallel normal faults mineralization principally in Combined Metals bed of the Pioche Shale. Highland Peak overthrust

Type: L
Description: steeply dipping fissures: N50-70E mineralized zone

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Alterations

Alteration Type: L
Alteration Text: oxidation; hydrothermal

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Rocks

Name: Limestone
Role: Associated
Age Type: Associated Rock
Age Young: Early Ordovician

Name: Shale
Role: Associated
Age Type: Associated Rock
Age Young: Middle Cambrian

Name: Porphyry
Role: Host
Description: granite dikes
Age Type: Host Rock
Age Young: Tertiary

Name: Limestone
Role: Associated
Age Type: Associated Rock
Age Young: Early Ordovician

Name: Dolomite
Role: Associated
Age Type: Associated Rock
Age Young: Late Devonian

Name: Dolomite
Role: Associated
Age Type: Associated Rock
Age Young: Middle Devonian

Name: Dolomite
Role: Associated
Age Type: Associated Rock
Age Young: Late Ordovician

Name: Quartzite
Role: Associated
Age Type: Associated Rock
Age Young: Late Ordovician
Age Old: Middle Ordovician

Name: Granite
Role: Host
Description: porphyry dikes
Age Type: Host Rock
Age Young: Tertiary

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Middle Cambrian

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Early Ordovician
Age Old: Late Cambrian

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Middle Cambrian

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Early Cambrian

Name: Quartzite
Role: Host
Age Type: Host Rock
Age Young: Early Cambrian
Age Old: Neoproterozoic

Name: Limestone
Role: Associated
Age Type: Associated Rock
Age Young: Pennsylvanian
Age Old: Mississippian

Name: Quartzite
Role: Associated
Age Type: Associated Rock
Age Young: Late Mississippian

Name: Siltstone
Role: Associated
Age Type: Associated Rock
Age Young: Late Mississippian

Name: Limestone
Role: Associated
Age Type: Associated Rock
Age Young: Early Mississippian

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Analytical Data

Not available

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Materials

Ore: Argentite
Ore: Pyrite
Ore: Sphalerite
Ore: Gold
Ore: Chalcopyrite
Ore: Galena
Ore: Cerussite
Ore: Cerargyrite
Gangue: Calcite
Gangue: Siderite
Gangue: Jarosite
Gangue: Limonite
Gangue: Quartz

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Comments

Comment (Deposit): The main orebody at the Caselton, Raymond & Ely/Combined Metals Reduction #1 mines is the result of selected replacement of the Combined Metals Limestone bed where it intersects the steeply-dipping Greenwood Fissure, which is a fault of slight displacement, usually expressed as a thin gouge seam but which may be up to 5 feet thick. It trends N70E, and dips 65-70N, nearly paralleling the Raymond and Ely vein, which dips 75S. The ore has been offset by many cross-faults the main orebody is a tabular massive sulfide bed extending laterally into the limestone layer, thickest (30-40 feet) adjacent to the Greenwood Fissure, and tapering down away from it. Bedded ore occurs up to 200 feet on either side of the Greenwood Fissure. The ore of the upper bed preserves the nodular character of the limestone host. Ore consists of about 60% pyrite, 22% sphalerite, 8% galena, minor chalcopyrite and practically no gangue minerals. The lower bed ore is massive with an irregular bottom contact, as the underlying quartzite has been irregularly replaced by pyrite and sphalerite. The ore is unoxidized. The Raymond and Ely vein in the Prospect Mountain Quartzite strikes parallel to the Greenwood Fissure. The Greenwood ore occurs chiefly in Pioche Shale. The Black Ledge vein of quartz and sphalerite was also mined yielding 12-20% zinc and 5-21 ounces of silver per ton. The Raymond and Ely vein system splits eastward into two branches: the Meadow Valley vein and the Burke Vein. The largest and richest ore shoot in the vein occurred just below the Pioche Shale within about 400 feet of the Yuba Dike. The complex sulfide ore was of no value until selective flotation was invented. The ore bed was mined for more than 10,000 feet along an east west channel 100 to 1800 feet wide. Ore body terminates against the frontal fault. The hanging wall was unsuccessfully explored to a depth of 2500 feet. Most gold came from the Combined Metals Mine. On Treasure Hill, the workings explore a series of faults and shears and the north end of the Yuba dike, a principal contributor to the mineralization of the area. Much of the fault breccia shows milling texture with jarosite and iron-manganese oxides coating most exposed surfaces. The quartzite ranges from white to grey-rose colored with prominent banding. Pods of very fine-grained argentiferous minerals along with galena and other sulfides are disseminated throughout the breccia. Yellow oxides are also common on exposed surfaces. Abundant sericite is present. Locally the breccia zones are silicified and abundant gossan occurs where ore minerals have weathered out. Late opaline silica is deposited on fracture surfaces and iron sulfides have altered to specular hematite. Euhedral quartz crystals line cavities. Quartz vein material which fills fault fissures exhibits brecciation and is recemented with silica, and contains bands of finely disseminated grey sulfides. The Raymond and Ely, Meadow Valley, and Burke veins strike roughly east-west and dip 50 degrees south. Oxidized silver ore in the quartzite decreased in grade eastward and downward. The Meadow Valley vein was mined continuously for 2000 feet to a depth of 1,200 feet. Average ore thickness was 2-3 feet. Galena and sphalerite are increasingly abundant in the lower levels. Rich silver-lead ore was mined from the Yuba Dike. Three or more cross veins strike northeast at 45 degrees to the principal veins. The "quartzite fissures" are veins with filling of loose rubble of angular quartzite fragments to breccia cemented by lead carbonate, limonite, and jarosite. The quartzite fissures strie N15-20W.

Comment (Development): The initial mineral discovery in Pioche occurred in 1863 and mining production began in 1869. The original ore consisted of oxidized silver chlorides occurring in fissures in Cambrian quartzites. The Raymond and Ely vein system contained high-grade lead-silver ore that was mined in the 1870s At one time Pioche was one of largest silver districts in the United States. Total mineral production exceeded $130,000,000. The primary metal values were for gold, silver, lead, zinc and copper. Low-grade argentiferous manganese oxides were also found in the region. Major periods of production were: 1895-1901; 1912-1920; 1934-1953; and 1958-1959. Minimal activity has occurred from 1959 to the present time. Early milling occurred in Pioche, but a shortage of water forced the mills to be relocated to Bullionville (near Panaca) around 1871. In 1924 Combined Metals Reduction Company developed a selective flotation process to treat the massive lead-zinc sulfide ores. Combined Metals Reduction Company processed ore at a mill in Bauer, Utah from 1923-1941, until the Caselton Mill was built in 1941. Mountain Mines, Inc. acquired the Caselton Tailings after the bankruptcy of Combined Metals Reduction Company in 1976. Mountain Mines, Inc. claims to have produced precious metals from the tailings with a small chemical processing facility located in the vicinity of the tailings. Numerous mining companies have had operators or exploration activity at site, including: Meadow Valley Mining Company (1864-1876); Consolidated Mining Company (1880's); White Pine Minerals Company (?); Combined Metals Reduction Company (1924-present); Pioche Manganese Company (WWII); Comet Coalition Mining Company (1964-1978); St. Patrick Mining Company (1975); Bunker Hill Mining Company (1976-77); Kerr-McGee Chemical Company (1980); Mountain Mines, Inc. (1976-present). Homestake Mining Company, Prince Consolidated Mining Company and Anaconda Company also have been active in the area. Midway Gold Company has recently (2004) been exploring for a faulted offset of the high-grade silver-gold Salt Lake Pioche vein under post- mineral volcanic rock. The property consists of five patented and 36 unpatented claims lying south of the town of Pioche on a combination of private patented mining claims and BLM administered lands. Midway began a 3500 foot reverse circulation drill program on the Pioche Project in October 2004.

Comment (Economic Factors): From 1905 to 1958 the total production from the Pioche district mines was 810,366 ounces of gold, 17,956,492 ounces of silver, 6,254,900 pounds of copper, 317,007,800 pounds of lead, 640,224,100 pounds of zinc, and 711,400 tons of manganese ore. 1869 to 1904 production was not broken down. Reserves: 1958: Caselton type ore: 2,642,830 metric t (includes production) 0.046 opt Au, 5.32 opt Ag, 4.81% Pb, 11.82% Zn; Pan American type ore: 149,629 metric t, 0.028 opt Au, 1.64 opt Ag, 1.39% Pb, 2.66%Zn, 9.7% Mn 1952: Caselton type ore: 674,300 metric t (includes production) 0.013 opt Au, 0.65 opt Ag, 0.6% Pb, 9.5% Zn, 0.4% Cu 1949: Caselton type ore: 197,921 metric t (includes production) 0.035 opt Au, 3.21 opt Ag, 1.24% Pb, 9.7% Zn, 0.14% Cu; 12.32% Mn (oxidized ore); 31.5% Fe (oxidized ore)

Comment (Commodity): Ore Materials: argentite, cerargyrite, cerussite, galena, pyrite, sphalerite, chalcopyrite, gold

Comment (Identification): This is a new record that includes all material in earlier MRDS record W002906, other earlier MRDS records for theindividual deposits, as well as additional new information.

Comment (Location): The Pioche District mines are scattered over a few square miles in the Pioche Hills (including Treasure Hill) west, southwest, and south of Pioche.

Comment (Workings): The veins were developed by extensive underground workings; shafts, adits, trenches, cuts, and prospect pits. Most of the old underground workings were caved by the 1980s. There was a small open pit and heap-leach operation working in the 1980s. Water was in the old workings at the 1200 foot level.

Comment (Geology): The Combined Metals Member of the Pioche Shale is the host rock for the replacement orebodies. It consists of 3 parts: (1) a lower 3 ft of massive limestone (2) a middle 3-ft thick calcareous sandstone (which in the orebody is unreplaced) and (3) an upper 30-ft layer of thin-bedded nodular limestones, usually only 2-3 inches thick and so nodular that they look like "beds of flattened potatoes". The nodules are coated with a thin black carbonaceous skin. The Pioche Shale belt trends NW between 2 faults.

Comment (Commodity): Gangue Materials: quartz, calcite, siderite, jarosite, limonite

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References

Reference (Deposit): Pack, F. J., 1906, Geology of Pioche, Nev., and Vicinity: Nev. School of Mines Quart. Vol. 27 Nos. 3 and 4, pp. 281-333

Reference (Deposit): Koschmann, A. H. and Bergendahl, M H, 1968: Principal Gold Producing Districts of The United States: USGS Prof. Paper 610

Reference (Deposit): Westgate, L G. and Knopf, A., 1932, Geology and Ore Deposits of the Pioche District, Nevada: USGS Prof. Paper 171, 79p.

Reference (Deposit): State of Nevada Interagency Abandoned Mine Land Environmental Task Force (IAMLET), 1999, report, http://www.nv.blm.gov/AML/IAMLETreport.htm.
URL: http://www.nv.blm.gov/AML/IAMLETreport.htm

Reference (Deposit): Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Database of significant deposits of gold, silver, copper, lead, and zinc in the United States; Part A, Database description and analysis; part B, Digital database: U.S. Geological Survey Open-File Report 98-206, 33 p., one 3.5 inch diskette.

Reference (Deposit): NBMG MI-80

Reference (Deposit): James, L.P., and Knight, L.H., 1979, Stratabound lead-zinc-silver ores of the Pioche District, Nevada - Unusual "Mississippi Valley" Deposits; in RMAG-UGA 1979 Basin and Range Symposium proceedings.

Reference (Deposit): Tschanz, C. M. and Pampeyan, E. E., 1970, Geology and Mineral Deposits of Lincoln Co., Nev,: Nev. Bur. of Mines Bull. 73 p. 125-129.

Reference (Deposit): Lincoln, F. C., 1923, Mining Districts and Mineral Resources of Nevada: Reno, Nevada Newsletter Pub. Co., p. 125-129

Reference (Deposit): Anderson, J. C., 1922, Ore Deposits of Pioche Dist: Eng & Min Jour, Vol. 113, p. 279-85.

Reference (Deposit): Hill, J M, 1916, Notes on some Mining Districts in E. Nev.: USGS Bull. 648, p. 124-137.

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Nevada Gold

Nevada has a total of 368 distinct gold districts. Of the of those, just 36 are major producers with production and/or reserves of over 1,000,000 ounces, 49 have production and/or reserves of over 100,000 ounces, with the rest having less than 100,000 ounces. Read more: Gold Districts of Nevada.