Mount Hope Molybdenum Deposit

Site Name

Primary: Mount Hope Molybdenum Deposit

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Commodity

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

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Location

State: Nevada
County: Eureka
District: Mount Hope 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: Idaho General Mines, Inc.
Info Year: 2005

Owner Name: Mount Hope Mines, Inc.
Info Year: 2005

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Past Producer
Deposit Type: pluton-related porphyry molybdenum
Operation Type: Surface-Underground
Year First Production: 1880
Year Last Production: 1940
Discovery Year: 1870
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: Climax Mo

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Orebody

Form: irregular

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Structure

Type: R
Description: Roberts Mountains Thrust fault

Type: L
Description: Host rocks in the deposit area are cut by several faults: the N35W-trending Ravine Fault, the N60W-trending Bisoni Fault, the N80W-trending Tia Fault, and the N75W-trending South Fault. The Mount hope Fault is arcuate, changing orientation dramatically from about N30E north of the mine area to N75W south of the mine area, with the ?bend? in the fault occurring in the vicinity of the molybdenum deposit.

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Alterations

Alteration Type: L
Alteration Text: Skarn development, tactite-hornfels at the historic lead zinc deposits. The porphyry molybdenum deposit is characterized by a variety of alteration assembages attendant upon the mineralization.These include argillic-propylitic, argillic, potassic-phyllic, potassic, silica-flooded, and bioite zones, roughly concentrically zoned outward from the core of the hydrothermal system.

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Rocks

Role: Associated
Age Type: Associated Rock Unit
Age Young: Tertiary

Role: Associated
Age Type: Associated Rock Unit
Age Young: Tertiary

Name: Argillite
Role: Associated
Age Type: Associated Rock
Age Young: Permian

Name: Chert
Role: Associated
Age Type: Associated Rock
Age Young: Permian

Name: Shale
Role: Associated
Age Type: Associated Rock
Age Young: Tertiary

Name: Rhyolite
Role: Associated
Age Type: Associated Rock
Age Young: Tertiary

Name: Alkali-Granite (Alaskite)
Role: Associated
Age Type: Associated Rock
Age Young: Tertiary

Role: Host
Age Type: Host Rock Unit
Age Young: Early Permian

Role: Host
Age Type: Host Rock Unit
Age Young: Ordovician

Name: Granite
Role: Host
Description: (molbdenum deposit)
Age Type: Host Rock
Age Young: Tertiary

Name: Limestone
Role: Host
Description: (historic workings)
Age Type: Host Rock
Age Young: Permian

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Analytical Data

Not available

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Materials

Ore: Molybdenite
Ore: Chalcopyrite
Ore: Pyrrhotite
Ore: Galena
Ore: Sphalerite
Ore: Marmatite
Ore: Bornite
Gangue: Magnetite
Gangue: Pyrite
Gangue: Calcite
Gangue: Tremolite
Gangue: Quartz
Gangue: Diopside
Gangue: Garnet
Gangue: Hematite

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Comments

Comment (Location): The Mount Hope Molybdenum Deposit is centered on the south to southeast flank of Mount Hope.

Comment (Workings): Historic workings consist of four separate workings: the Lorraine area; the Whim Shaft; Mt. Hope #1 Shaft and Mount Hope #2 Adit. Numerous roads and drill pads date from the 1980s molybdenum exploration. Exxon's porphyry molybdenum discovery was to be mined as an open pit operation.

Comment (Deposit): Ore deposits occur near the contact of an alaskite stock with the carbonate rocks it intrudes. Ore of the historic lead-zinc deposits occurs as replacement bodies in limestone roof pendants. Significant molybdenum mineralization is mainly confined to Vinini hornfels and several phases of quartz porphyry intrusive. The mineralization forms two adjacent inverted cone-shaped double shells.

Comment (Commodity): Ore Materials: Molybdenite, bornite, marmatite, blackjack, galena, pyrrhotite, chalcopyrite

Comment (Commodity): Gangue Materials: garnet, diopside, quartz, tremolite, calcite, pyrite, magnetite, hematite

Comment (Economic Factors): Total lead-zinc mine production valued at $1,335,393 as of 1964. Feasibility studies in the l980s targeted mining 205 million tons of ore grading 0.11 percent molybdenum (2.2 pounds molybdenum per ton) by open pit methods to recover approximately 400 million pounds of molybdenum. Mount Hope is considered by the USGS to be one of the ?Giant Porphyry-Related Metal Camps of the World?

Comment (Geology): The historic lead-zinc mine workings explore the contact between an alaskite stock with the carbonates of the Garden Valley Formation. Ore occurs as replacement deposits in limestone roof pendants. Large areas of skarn have been developed in the shales and carbonates.

Comment (Development): Exploration began in the Mount Hope area in 1871 following the discovery of lead-zinc ore by charcoal producers for the Eureka and Palisade Railroad and the Eureka smelters. The district was first called MmcGarry (McGeary) but was unsuccessful and died out, later to be revived as the Mount Hope District in the mid 1880s. The Lorraine workings were opened in 1886 and local lawyer Thomas Wren sank the Mt. Hope #2 adit and whim shaft in the early 1890s. The main periods of development at Mount Hope were from 1936-1938 and 1946-1949 when housing for the mineworkers was erected on site. The area was explored by the U.S.B.M. in 1946. Renewed exploration for molybdenum by Exxon Co., USA in the late 1970s and early 1980s outlined a sizeable porphyry molybdenum orebody of mineable grade in the Mount Hope area. In November 2004 Idaho General Mines, Inc. (IGMI) announced that an agreement had been signed with Mount Hope Mines, Inc. whereby IGMI has been granted an exclusive one year option to lease Mount Hope's previously drilled molybdenum deposit in Eureka County, Nevada. This option to lease, exercisable by Idaho General Mines at anytime in the first year, allows IGMI to invoke a pre-negotiated 30 year (extendable) lease on the property upon exercise. The property consists of 13 patented claims and 109 unpatented claims. In addition 350 adjoining claims have now been located and made a part of the property. IGMI has access to an extensive data base of drilling and feasibility work accomplished by several major mining companies during the 1980's. The drilling of 135 diamond drill holes delineated an extensive porphyry molybdenum deposit that is geologically similar to the large molybdenum deposits at the famous Climax and Henderson Mines in Colorado. The drilling at Mount Hope identified 630 million tons grading .085 percent molybdenum. A higher-grade central area at relatively shallow depth was extensively drilled. Feasibility studies in the l980s targeted mining 205 million tons grading 0.11 percent molybdenum (2.2 pounds molybdenum per ton) by open pit methods to recover approximately 400 million pounds of molybdenum. IGMI will complete a pre-feasibility study over the next four months that targets mining this higher-grade core at over 25,000 tons per day. Metallurgical studies indicate a high recovery of the metal through conventional process.

Comment (Identification): This Mount Hope Molybdenum Deposit covered by this record encompasses the original Mount Hope lead-zinc mine deposit originally described by earlier MRDS record M232308, and includes additional information pertinent to the current Mount Hope porphyry molybdenum deposit.

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References

Reference (Deposit): Numerous unpublished items in NBMG mining district files available online at www.nbmg.unr.edu

Reference (Deposit): Felix E. Mutschler, Steve Ludington, and Arthur A. Bookstrom, 1999, Giant Porphyry-Related Metal Camps of the World-A Database; USGS Open-File Report 99-556.

Reference (Deposit): Idaho General Mines, Inc. website, Feb. 2005; http://www.idahogeneralmines.com/igmidir/news/news111504.htm
URL: http://www.idahogeneralmines.com/igmidir/news/news111504.htm

Reference (Deposit): Numerous unpublished items in NBMG mining district files available online at www.nbmg.unr.edu

Reference (Deposit): Vanderburg, W. O. (1938) Reconnaissance of the Mining Districts in Eureka Co., USBM Inf. Cir. 7022

Reference (Deposit): Matson, E. J. (1946) Exploration of the Mount Hope Mine, Eureka Co. Nev., U.S. Bureau of Mines R. I. 3928

Reference (Deposit): U.S. Bureau of Mines (Millett) MILS No. 132, Ref. No. 3201100037, Mineral Property File 79.004

Reference (Deposit): Roberts, R. J., et al. (1967) Geology and Mineral Resources of Eureka Co., Nev., NBMG Bull. 64

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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.