Ruby Hill Gold Mine

Site Name

Primary: Ruby Hill Gold Mine
Secondary: West Archimedes Deposit
Secondary: East Archimedes resource
Secondary: Archimedes Gold deposit

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Commodity

Primary: Gold
Secondary: Silver
Tertiary: Arsenic
Tertiary: Mercury
Tertiary: Antimony
Tertiary: Zinc
Tertiary: Barium-Barite

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Location

State: Nevada
County: Eureka
District: Eureka District

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Land Status

Land ownership: BLM Administrative Area
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: Battle Mountain BLM District

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Barrick Gold Corp
Info Year: 2006

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: sediment-hosted gold
Operation Type: Surface
Year First Production: 1997
Discovery Year: 1991
Years of Production:
Organization:
Significant: Y
Deposit Size: M

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Physiography

Not available

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Mineral Deposit Model

Model Name: Sediment-hosted Au

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Orebody

Form: The deposit shape is complex and irregular, but generally has a central elongate, subtabular body with ovate cross section. From this core, similar shaped lithologically controlled lobes branch and flare out along structural intersections.

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Structure

Type: R
Description: Roberts Mountains Thrust; Central Nevada Fold Belt; Hoosac Thrust

Type: L
Description: The oldest identified structures within the deposit are the high-angle NNE-trending Bowman, ?271?, and Jackson pre-mineral faults that were important in localizing some gold mineralization. More common within the deposit are WNW-trending high angle structures including the Blanchard fault system, which largely controlled emplacement of the West Archimedes deposit, and the Molly fault system, which localized some gold mineralization and had up to 100m of post-mineral offset. E-W-trending normal faults localized base metal mineralization, and NNW-trending faults (such as the Holly and the ?150?) show significant post-mineral offsets, and may be associated with regional basin-and-range development.

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Alterations

Alteration Type: L
Alteration Text: Zones of silicification, jasperoid development, and limestone decalcification (decarbonization) guided ore formation.

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Rocks

Name: Limestone
Role: Host
Description: fine to coarse
Age Type: Host Rock
Age Young: Early Ordovician
Age Old: Middle Ordovician

Name: Chert
Role: Host
Age Type: Host Rock
Age Young: Early Ordovician
Age Old: Middle Ordovician

Name: Porphyry
Role: Host
Description: quartz-feldspar
Age Type: Host Rock
Age in Years: 110.000000+-5.000000
Dating Method: K-Ar
Material Analyzed: whole rock
Age Young: Early Cretaceous

Name: Limestone
Role: Host
Description: micritic to shaley
Age Type: Host Rock
Age Young: Early Ordovician
Age Old: Middle Ordovician

Name: Limestone
Role: Host
Description: cherty
Age Type: Host Rock
Age Young: Early Ordovician

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Analytical Data

Not available

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Materials

Ore: Gold
Ore: Electrum
Ore: Limonite
Ore: Hematite
Ore: Pyrite
Ore: Cinnabar
Ore: Barite
Gangue: Quartz

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Comments

Comment (Commodity): Gangue Materials: quartz, limonite, hematite, pyrite, cinnabar, barite, various sulfide minerals

Comment (Deposit): Archimedes is a Carlin-style sediment-hosted gold deposit in carbonate rocks. The ore is a mixture of jasperoid and decalcified limestone exhibiting strong structural controls. Micron-size gold is associated with oxidized pyrite sites and is strongly fracture controlled. Deeper portions of the east Archimedes resource are sulfidic, and root-zones include retrograde-altered base metal skarn and marble hosts. The mineralized area closely adjoins a Cretaceous porphyry intrusive and may be genetically linked to it, as both base metal-related adularia and the intrusive yield similar radiometric ages. Some evidence suggests the presence of a younger cross-cutting Au-As-Hg system superimposed on the earlier base-metal system and associated with Oligocene magmatism. The West Archimedes deposit is about 780 m long, plunging gently S60?E and covered by 15 to 150 m of partially cemented calcareous alluvium. The deposit is subtabular to ovate in cross section, branching locally at structural intersections. The orebody has a central elongated lens of higher grade jasperoid ore enclosed by a more tabular envelope of lower grade decalcified limestone ore.

Comment (Commodity): Commodity Info: Mercury is retorted from process metal sludge.

Comment (Commodity): Ore Materials: gold, electrum

Comment (Development): The initial discovery sample was collected in 1991 by a geologist working under contract to Homestake from a pit north of the old Holly Extension mine dump. The first hole was drilled in the orebody in 1992, and an economic deposit was indicated by mid-1993. The Archimedes orebody was discovered by rock-chip sampling and subsequent geochemical soil anomaly and drilling. Stripping of the Archimedes deposit began in early 1997, and the first gold was poured on November 6,1997. By year?s end, the mine had reached expected production of 3,500 tons per day, of which about 2,600 tons of lower-grade ore is heap leached, while 900 tons of higher-grade material is sent to the mill. The stripping ratio is 7-to-1 and anticipated production is between 105,000 and 110,000 troy ounces of gold annually. Exploration in 1998 continued in the immediate area to identify other shallow oxide deposits as well as a deep drilling program designed to further define a zone of high grade sulfide mineralization discovered 1,500 feet below the West Archimedes open pit. By 2005, Barrick reported that thecurrent project will be an open-pit, heap leach operation exploiting the East Archimedes deposit, a deeper continuation of the ore mined previously at Ruby Hill. Permitting has been secured and the two-year, approximately $75-million construction phase is underway. The project is expected to enter production in early 2007 and has reserves of 1.0 million ounces at December 31, 2005.

Comment (Location): The east edge of the Archimedes deposit is on the east flank of Mineral Point, between the old Holly and Holly Extension mine workings less than one mile northwest of downtown Eureka.

Comment (Workings): The West Archimedes deposit of the Ruby Hill Gold Mine is developed by an open pit in an area previously mined for polymetallic deposits by underground methods. A mill, haul roads, leach pads, and waste dumps are also present on the property

Comment (Economic Factors): Ruby Hill production for 1997 was 16,600 ounces of gold. Total production through April, 1998 was about 57,000 ounces of gold. Recent dore has contained less than 10% silver. In early 1998, reserves stand at 7.028 million tons proven and probable ore grading 0.098 opt gold plus 7.173 million tons mineralized material grading 0.073 opt gold. IN 2006, Barrick reports reserves of 1.0 million ounces for the East Archimedes deposit, scheduled to begin production in 2007.

Comment (Geology): The primary host rock of the Archimedes deposit is thin to thick bedded cherty limestone of the early Ordovician Goodwin Limestone of the Pogonip Group. minor hosts are micritic to shaley limestone of the early Ordovician Ninemile Formation also of the Pogonip Group, and early Cretaceous quartz porphyry. Archimedes satellite deposits are hosted by fine- to coarse early to middle Ordovician limestone and chert of the Antelope Valley Limestone, also of the Pogonip Group. The West Archimedes deposit is a more stratigraphically controlled offshoot of the East Archimedes deposit, a steeply-plunging, oxidized, gold-bearing jasperoid breccia adjoining the quartz-feldspar porphyry intrusive.

Comment (Identification): The names Ruby Hill Gold Mine and Archimedes Gold Deposit refer to the same operation. This record supersedes the incomplete Archimedes MRDS record MP90056 which should be deleted. All data from the MP90056 record has been incorporated into this new record.

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References

Reference (Deposit): Dilles, P.A., Wright, W.A., Monteleone, S.E., Russell, K.D., Marlowe, K.E., Wood, R.A., and Margolis, J., 1996, The geology of the West Archimedes deposit: a new discovery in the Eureka mining district, Eureka County, Nevada, in Coyner, A.R., and Fahey, P.L., eds., Geology and Ore Deposits of the American Cordillera: Geological Society of Nevada Symposium Proceedings, 1995, Reno/Sparks, Nevada, v. 1, p. 159-171.

Reference (Deposit): Russell, K., 1996, West Archimedes Gold Deposit, in Green, S.M., and Struhsacker, E., eds., Geology and Ore Deposits of the American Cordillera: Geological Society of Nevada Field Trip Guidebook Compendium, 1995, Reno/Sparks, NV, p. 316-319.

Reference (Deposit): Sediment-hosted Gold Deposits of the Eureka (Ruby Hill Mine) and Gold Bar Districts, East-Central Nevada, Geological Society of Nevada Special Publication No., 27, 1998 Spring Field Trip Guidebook.

Reference (Deposit): NBMG MI-97

Reference (Deposit): Mining Engineering, Dec., 1994, Society for Mining, Metallurgy, and Exploration, Littleton, Co, vol. 46, p. 1320.

Reference (Deposit): Final Environmental Impact Statement for the Ruby Hill Project of Homestake Mining Company, January 1997.

Reference (Deposit): Homestake press release, 2/19/98

Reference (Deposit): Denver Mining Record, 12/3/97

Reference (Deposit): Northern Miner, 11/23/97

Reference (Deposit): Long, K.R., DeYoung, J.H., Jr., and Ludington, S.D., 1998, Significant deposits of gold, silver, copper, lead, and zinc in the United States: U.S. Geological Survey Open-File Report 90-206A, 33 p.; 98-206B. one 3.5 inch diskette.

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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.