Mill City Tungsten Mine

Site Name

Primary: Mill City Tungsten Mine
Secondary: Springer Mine
Secondary: Humbolt-Springer
Secondary: Humbolt Mine
Secondary: Nevada-Massachusetts Mine
Secondary: Stank and Forge Lease
Secondary: Summit Mine
Secondary: Codd Mine
Secondary: O'Byrne Mine
Secondary: Keyes Shaft
Secondary: Friedman
Secondary: Constantine
Secondary: Sutton
Secondary: North Sutton
Secondary: Sutton No. 2
Secondary: Orphan
Secondary: South Sutton
Secondary: Baker Workings
Secondary: Uncle Sam Midway

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Commodity

Primary: Tungsten
Secondary: Molybdenum
Tertiary: Copper
Tertiary: Bismuth
Tertiary: Silver
Tertiary: Gold

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Location

State: Nevada
County: Pershing
District: Mill City 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: General Electric
Info Year: 2005

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: skarn; vein
Operation Type: Surface-Underground
Year First Production: 1918
Year Last Production: 1982
Discovery Year: 1917
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: W skarn

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Orebody

Not available

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Structure

Type: L
Description: The Stank fault strikes N-S for 1.5 miles. Strata strike N20E. The strata on the west side of the fault dip east, while on the east side of the fault, beds dip 70 west. Post-mineral faults also present, in many cases off-setting mineralized skarn beds.

Type: R
Description: Basin and Range faulting

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Alterations

Alteration Type: L
Alteration Text: silicification, albitization

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Rocks

Name: Andesite
Role: Associated
Description: hornblende-andesite dikes
Age Type: Associated Rock
Age Young: Tertiary

Name: Granodiorite
Role: Associated
Description: equigranular stock
Age Type: Associated Rock
Age in Years: 78.400000+-2.900000
Dating Method: K-Ar
Age Young: Late Cretaceous

Name: Limestone
Role: Host
Age Type: Host Rock
Age Young: Late Triassic

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Analytical Data

Not available

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Materials

Ore: Scheelite
Ore: Garnet
Ore: Diopside
Ore: Calcite
Ore: Tremolite
Ore: Wollastonite
Ore: Pyrite
Ore: Quartz
Ore: Garnet
Ore: Powellite
Ore: Quartz
Gangue: Epidote

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Comments

Comment (Commodity): Ore Materials: scheelite, powellite

Comment (Commodity): Gangue Materials: epidote, garnet, quartz, pyrite, wollastonite, tremolite, calcite, diopside, garnet, quartz

Comment (Economic Factors): Production from 1925-1944 totalled 1,049,714 tons of ore with an average grade of 1.17% WO3, yielding 1,100,773 units WO3. From 1944 to 1958, production totalled 2,073,565 tons of ore grading 042% WO3, for a total yield of 685,365 units WO3. The sharp drop in ore grade was due to a change from mining the richer ore of the Stank and Humboldt orebodies to the lower grade Sutton orebodies in 1944 and the addition of large low-grade tonnages from open pits in the 1950s which averaged 0.22-0.25% WO3. The total recorded production from the Mill City District mines for the productive year between 1917 and 1958 was 3,258,135 tons of ore yielding about 2.2 million units of WO3. In 1982, General Electric announced 13-15 years worth of ore reserves at the Mill City mines, which were not depleted before they closed operations in October of that year.

Comment (Geology): The Stank orebody appears to be a pendant-like mass. Triassic sediments are intruded by granodiorite stocks and dikes, producing contact metamorphism (garnet-epidote-wollastonite-tremolite). These were followed by andesite dikes.

Comment (Development): Although the Eugene Mountains were mined for silver and gold beginning in 1862, tungsten was not discovered there until Emil Stank had a sample analyzed that he had collected while silver prospecting a few years earlier. The onset of World War I had increased demand for tungsten, and Stank?s discovery was rapidly brought into production by three companies within months of the claim locations. Pacific Tungsten Company took over Stank?s claims, Thomas Sutton formed the Mill City Tungsten Mining Company to work his claims east of , and L. T. Friedman formed the Nevada-Humboldt Mining Company to mine the deposits on Humboldt Hill. Two of the companies were operating mills by the end of 1918, but the end of the war brought the cessation of tungsten mining at Mill City in 1919. By 1925, the Nevada-Massachusetts Company under Charles Segerstromhad purchased and consolidated all of the main district properties and was the sole operator at the Tungsten camp until 1958 when production ceased. The property was maintained on standby until 1962,after which it slipped into disrepair. In 1969, however, Segerstrom?s heirs, operating under Tungsten Properties Limited partnership, again acquired the property and in 1971 negotiated a deal with General Electric Co. to re-evaluate the property. After extensive explorration and development, GE constructed a $55 million mine, mill, and processing plant, which operated for less than a year in 1982, at which time depressed prices forced closure again. For more than 20 years, the mine has been kept in ?mothballs? with a caretaker to maintain equipment in working condition. A buyer was being sought (2005) to reopen the mine since it is in a ?turnkey? state ready to be brought back into production will minimal renovation.

Comment (Deposit): The scheelite deposits of the district occur in roughly parallel limestone beds that have been altered to skarn. The main production has been from a few distinct beds that traverse the district with a general northerly trend. The main production zone is about a mile long and about 0.75 mile wide bounded on the north by the Olsen stock. The southern boundary is more gradational, governed by proximity to the Springer Stock. Virtually all district tungsten production has come from mines on five ore beds: the Humboldt, Springer, and Stank ore horizons, and the Sutton No. 1 and Sutton No. 2 mines on the Sutton horizon. The Summit-O'Byrne bed strikes NE, dips steeply SE and extends from the south rim of the George Mine pit across Stank Hill and into Stank Canyon, where it comes in contact with the small southwest stock. Ore in the tactite body was limited to a triangular segment of the bed lying between the surface and the plane of the Stank fault. Ore on the south was limited by the gradational limestone-tactite boundary. Scheelite occurs as disseminations and fracture coatings in skarn bodies and as irregular blebs and crystal masses in quartz veins that cut through the skarn and granodiorite. Scheelite is the main ore mineral, accompanied in places by small amounts of molybdenite, chalcopyrite, rare bismuthinite, and up to several percent pyrite. Powellite occurs only as a secondary mineral associated with molybdenite.

Comment (Identification): This is a new record encompassing information from many earlier records for individual shafts or prospects on the tungsten deposits of the central Mill City District.

Comment (Location): The mine workings are located about 8 miles NNW of Mill City spread out on the flanks of Stank Hill, Springer Hill and Humboldt Hill near the lower part of Springer Canyon.

Comment (Workings): The mine area is developed by many underground workings: shafts, drifts, stopes, amswell as by open pits at the surface. The Stank mine workings connect at the 300 level with those of the Springer Mine.

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References

Reference (Deposit): Kerr, P.F., 1934, Geology of the tungsten deposits near Mill City, Nevada, U. of Nev., Vol 28, No. 2 (NBMG Bull.21), 46 p.

Reference (Deposit): Johnson, M.G., 1977, Geology and Mineral Deposits in Pershing County, Nevada: NBMG Bull. 89

Reference (Deposit): Kerr, 1946, Tungsten Mineralization in the United States: GSA Memoir 15, 241 p.

Reference (Deposit): Stager, H. K and Tingley, J.V., 1988, Tungsten Deposits in Nevada, NBMG Bull. 105.

Reference (Deposit): King, W. H. and Holmes, G.H., Jr., 1950, Investigation of Nevada-Massachusetts Tungsten Deposits, Pershing County, NV; USBM Report of Investigations RI 4634, p. 3-4.

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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.