Rio Tinto Mine

Site Name

Primary: Rio Tinto Mine
Secondary: Mountain City Copper Mine
Secondary: Mountain City Silver Mine
Secondary: Mountain City Mercur
Secondary: Mountain City Consolidated.
Secondary: Golden Copper
Secondary: Golden Copper Nos. 1-3
Secondary: Rio Grande Copper
Secondary: Rio Grande North
Secondary: Rio Grande Extension
Secondary: Rio Grande Extension Nos. 1-7

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Commodity

Primary: Copper
Secondary: Silver
Secondary: Gold
Tertiary: Zinc
Tertiary: Lead

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Location

State: Nevada
County: Elko
District: Mountain 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.
Administrative Organization: Elko administrative district

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Holdings

Not available

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Workings

Type: Underground

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Ownership

Owner Name: E. I. Dupont Co.
Company ID: 2600210
Percent: 50.00
Home Office: Delaware
Info Year: 1974

Owner Name: Cliffs Copper (Div Of Cleveland Cliffs Iron Co.) (early 1970's)
Company ID: 2600210
Home Office: Denver, Colo
Info Year: 1974

Owner Name: Mountain City Consolidated

Owner Name: Cominco
Years: 1976 -

Owner Name: Mountain City Copper Co.

Owner Name: Rio Grande Copper Co.

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: massive sulfide
Operation Type: Underground
Year First Production: 1932
Discovery Year: 1919
Years of Production:
Organization:
Significant: Y
Deposit Size: S

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Physiography

Not available

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Mineral Deposit Model

Model Name: Massive sulfide, Besshi (Japanese deposits)

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Orebody

Form: tabular to irregular

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Structure

Type: R
Description: The Roberts Mountains Thrust fault is exposed at the surface less than 3 miles from the mine.

Type: L
Description: faults

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Alterations

Alteration Type: L
Alteration Text: Alteration types affecting the host rocks are chloritic, argillic, and silicic.

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Rocks

Name: Plutonic Rock
Role: Associated
Description: granitic
Age Type: Associated Rock
Age Young: Cretaceous

Name: Quartzite
Role: Host
Age Type: Host Rock
Age Young: Ordovician

Name: Shale
Role: Host
Description: dark
Age Type: Host Rock
Age Young: Ordovician

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Analytical Data

Not available

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Materials

Ore: Chalcopyrite
Ore: Azurite
Ore: Cuprite
Ore: Malachite
Ore: Galena
Ore: Sphalerite
Ore: Covellite
Ore: Chalcocite
Ore: Bornite
Ore: Copper
Gangue: Quartz
Gangue: Pyrite

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Comments

Comment (Development): In 1919, Samuel Franklyn Hunt, filed claims on some traces of copper a few miles south of Mountain City. He named his claims Rio Tinto after the famed copper mines in Spain and spent the next 12 years attempting to get financial backing to develop the claims. He was grubstaked during this time by Walt and Jack Davidson who ran a store in Mountain City. In 1931, Ogden Chase became interested in backing the venture, and Hunt and Chase organized the Rio Tinto Copper Company with Samuel Hunt as president and Ogden Chase as manager. In 1932 an inclined shaft was sunk and ore was hit at 227 ft. Production began in 1932. The ore assayed at 40% and gradually rose to 47%.On June 30, 1932, the International Smelting and Refining Company, a subsidiary of the Anaconda Copper Company, purchased the Rio Tinto Copper Company for $300,000. The company was renamed the Mountain City Copper Company. A flotation mill was built in 1937 to process the ore. It closed in 1949. In 1965, G.M. Wallace Co. of Denver leased the property from Bieroth, and leached copper from old tailings. Cliff's Copper Corp.of Rifle, Colo. purchased the mine in the early 1970s and continued leaching operations and did some underground work, investigating the feasibility of in-place leaching. The 1960s and early 1970s leaching operations yielded another 7.7 million pounds of copper. The mine closed again in 1975 with the fall in copper prices. Cominco bought the mine in 1976 but did not initiate any mining. The mill was dismantled for scrap by the Loveland Construction Company in 1979. Ore processing during historic mine operations included generated tailings that were emplaced in the Mill Creek drainage. In 1993, due to concerns about environmental damage to surrounding surface waters, four of the previous owners and operators of the site jointly formed the Rio Tinto Working Group (RTWG) to remediate the site in cooperation with the State of Nevada, Department of Conservation and Natural Resource and the Division of Environmental Protection (NDEP). The Rio Tinto Working Group consists of the Atlantic Richfield Company, Cleveland Cliffs Iron Company, E. I. DuPont de Nemours and Company, and Cominco American Inc. The RTWG was able to fast track site investigation and remedial designs, leading to a timely start up of remedial construction activities.

Comment (Geology): The Rio Tinto mine is developed in the Ordovician Valmy Formation. Several plutons of Cretaceous age intrude this and other Paleozoic formations; this sequence was eroded and covered with Miocene, Pliocene, and possibly older volcanic rocks. The primary mineralization of the area is believed to postdate the Mississippian Nelson Formation and pre-date the Cretaceous intrusives. The primary orebodies are lenticular in shape and are composed largely of quartz, pyrite, and chalcopyrite. The ore lenses, in general, strike northwestward and dip northward; they are in shales with associated minor quartzite lenses. The ore is epigenetic, and the principal orebody was leached to the 200-ft level; supergene copper sulfide ore was immediately below the barren gossan. The supergene enrichment of the ore may have required a large part of Tertiary time.

Comment (Identification): This record supersedes MRDS record #M233366 which should be deleted from the database. The current record includes all material from record #M233366

Comment (Location): The Rio Tinto mine is located in Copper Gulch, a few miles south of Mountain City.

Comment (Economic Factors): In summary, underground copper mining at Rio Tinto commenced in 1932 and continued intermittently for approximately forty years. From 1932 until operations ceased in 1949 the Rio Tinto mine produced 1,109,878 short tons of ore averaging 9.74% copper, 0.274 ounces per ton silver, and .0057 ounces per ton gold. Of this 177,043 tons averaged 26.1 per cent copper. Ore was leached from old tailings in the 1960's and 1970's yielding an additional 7.7 million pounds of copper. The site has not produced since 1975. There is no report of remaining reserves at the mine.

Comment (Deposit): The orebody is a hydrothermal exhalative massive sulfide replacement in the upper plate of the Roberts Mountains thrust fault. The original hypogene ore body consisted of quartz-chalcopyrite-pyrite and minor amounts of sphalerite and galena. The ore body is stratabound, it is limited to a particular sequence of black and gray shales with minor quartzite lenses. Supergene processes produced a gossan which was 400 feet by 100 feet at the surface and extends to a depth of 200 feet. Starting at approximately the 200 foot level and extending locally to below the 400 foot level secondary copper sulfides have formed. Locally these form a blanket from a few inches thick to 50 feet thick and in spots running as much as 50 percent copper. Below the zone of secondary sulfides is the primary quartz-chalcopyrite, pyrite ore. The ore body occurs in the upper plate of the Roberts Mountains thrust in eugeosynclinal rocks transported from the west. The primary orebodies are lenticular in shape and are composed largely of quartz, pyrite, and chalcopyrite. The ore lenses, in general, strike northwestward and dip northward; they are in shales with associated minor quartzite lenses. The ore is epigenetic, and the principal orebody was leached to the 200-ft level; supergene copper sulfide ore was immediately below the barren gossan.

Comment (Workings): The Rio Tinto mine was developed by underground workings on six levels.

Comment (Commodity): Ore Materials: chalcopyrite, bornite, chalcocite, covellite, sphalerite, galena, malachite, cuprite

Comment (Commodity): Gangue Materials: quartz, pyrite

Comment (Deposit): THE RIO GRANDE COPPER "WEST" CLAIM GROUP CONSISTS OF 4 CLAIMS: GOLDEN COPPER AND GOLDEN COPPER NOS. 1-3. THERE ARE CONTIGUOUS WITH THE WEST END OF THE RIO TINTO CLAIMS. THE RIO GRANDE COPPER "EAST" CLAIM GROUP CONSISTS 11 CLAIMS: RIO GRANDE NORTH, RIO GRANDE EXTENSION, RIO GRANDE EXTENSION NO. 1, RIO GRANDE, RIO GRANDE NOS. 1-7. THESE ARE CONTIGUOUS WITH THE EAST END OF THE RIO TINTO CLAIMS AND PARTLY WRAP AROUND THE EAST END. THE 1989 ELKO COUNTY MASTER TITLE PLATS SHOW THAT THE "WEST" CLAIMS ARE INCLUDED IN A MUCH LARGER CLAIM GROUP KNOWN AS THE PAT CLAIMS. THE PAT CLAIMS INCLUDE THE PAT NOS. 1-25, SPIRO CLAIMS, AND BJH CLAIMS. THE "WEST" CLAIMS ARE PARTLY INCLUDED IN THE LABERTA CLAIMS (ALBERTA-UTOPIA CLAIM GROUP) AND LUCKY NOS. 1-11 CLAIMS. PART OF THE "WEST" CLAIMS ARE NOW ON OPEN OR UNCLAIMED GROUND (1989).

Comment (Geology): THE MOUNTAIN CITY MINE ORE VEIN IS A FISSURE FILLING, CEMENTING ANGULAR FRAGMENTS OF LIMESTONE. AT SOME SITES THE VEIN IS SHEETED, CONTAING LIMESTONE PARTITIONS BETWEEN.

Comment (Development): AFTER 2 YRS RIO TINTO PREPROD MINE WILL HAVE A TOTAL LIFE OF 20 YRS, C ARE FOR AN IN-SITU-LEACH, ALL COSTS FROM L. MOORES NOTES. REC-120 + 151 BASE YR OF COSTING 1970. PHASE 1 MINING OPERATION - IN SITU LEACHING OF MINE TO 500 ANNUAL PRODUCTION 4,800,000 LBS, LIFE- 10.4 YRS NOTE- PROD. STARTED 1972 , SINK WELL BETWEEN 300 TO 500 L ELARGE PRESENT CEMENTATION PLANT ACQ 0 EXP $ 0 DEV 0 EQPT 244,600 LEACH PLANT 180,000 WORK CAP 200,100 OP COST (ANNUAL DIRECT, IND, TAX, INS) $605,100 PHASE 2 MINING OP - IN SITU LEACHING OF LOW GRADE ORE BRO UNDERCUTTING ANNUAL PRODUCTION 4,000,000 LBS COPPER, 10 YR LIFE NOTE- NEW WORK CONSISTS OF UNDERCUTTING ORE BLOCK AND DRIL SOLUTION DISTRIBUTION HOLES ABOVE CAVED ORE. MINE EQPT AND DEVEL $6,077,400 245,900 OP COSTS (ANNUAL DIRECT, IND, TAX, INS) $821,30 RESERVE ESTIMATE GIVEN FOR INDICATED ONLY-75% PROB INTERVAL 50% P I = 25% P I = 10% P I = 1.33 X 75% P I

Comment (Development): Mountain City mine: discovery year - 1820's, year first production - 1869, year last production - 1947, production years - 1869-1947.

Comment (Deposit): ACCORDING TO EMMONS, P. 84, SEVERAL HUNDRED THOUSAND DOLLARS WORTH OF SILVER ORE, SOME LEAD, WAS TAKEN FROM THE MOUNTAIN CITY MINE IN THE 1870'S, THROUGH A SHAFT, NOW INACCESSIBLE.

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References

Reference (Deposit): KIRKEMO, HAROLD, 1964, COPPER, IN MINERAL AND WATER RESOURCES OF NEVADA: NEVADA BUREAU OF MINES BULLETIN 65, P. 81-87 (Mountain City mine)

Reference (Deposit): NEV. BUR. OF MINES BULL. 54, 1957, PP. 120-122

Reference (Deposit): U.S. BUREAU OF MINES OPEN-FILE REPORT MLA 17-92, 1992, PLATE 1, NO. 20; PLATE 3, NO. 5.

Reference (Deposit): U.S. BUREAU OF MINES OPEN-FILE REPORT MLA 17-92, 1992, PLATE 1, NO. 21; PLATE 3, NO. 4. (Rio Grande Copper claims)

Reference (Deposit): RIDGE, JOHN D, 1972, ANNOTATED BIBLIOGRAPHY OF MINERAL DEPOSITS OF THE WESTERN HEMISPHERE, GSA MEMOIR 131, P 417-9.

Reference (Deposit): EMMONS, W.H., (1910) (Mountain City mine)

Reference (Deposit): USBM WAR MINERALS REPORT (UNPUBLISHED) OF THE RIO GRANDE COPPER (RIO TINTO) MINE, 1945, PROJECT 42 (ON FILE AT IFOC, DENVER FEDERAL CENTER)

Reference (Deposit): NBMG Mining District file mine maps #MD71, #M15

Reference (Deposit): Rio Tinto website:http://nvghosttowns.topcities.com/pastpro/riotinto.htm
URL: http://nvghosttowns.topcities.com/pastpro/riotinto.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): Basanez, 1979

Reference (Deposit): LaPointe and others, 1991, Mineral resources of Elko County, Nevada; NBMG Bull. 106

Reference (Deposit): Smith, R.M., 1976, Mineral Resources of Elko County, Nevada, U.S.G.S. Open File Rept. 1976-56

Reference (Deposit): Coats, R.R., and E.C. Stephens, 1968, Mountain City Copper Mine, Elko County, Nevada, in Ridge, J.D., Ed., Ore Deposits of The United States, 1933-1967 (Graton-Sales Volume), v.2: New York, Am. Inst, Mining Metall. Petroleum Engineers, p. 1074-1101.

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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.