Hog Ranch Mine

Site Name

Primary: Hog Ranch Mine
Secondary: Western Hog Ranch Mine
Secondary: Krista Pit
Secondary: East Deposit
Secondary: West Deposit
Secondary: Geib Pit
Secondary: Bell Spring Deposit
Secondary: Airport orebody
Secondary: 139 orebody
Secondary: White Mountain orebody
Secondary: NBMG Sample Site 2410

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Commodity

Primary: Gold
Primary: Silver
Tertiary: Mercury
Tertiary: Uranium

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Location

State: Nevada
County: Washoe
District: Leadville District (closest)

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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: Susanville BLM District

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Romarco Minerals Inc.
Info Year: 2004

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Production

Not available

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Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: Hot spring epithermal
Operation Type: Surface
Year First Production: 1986
Year Last Production: 1995
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: Hot-spring Au-Ag

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Orebody

Form: disseminated

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Structure

Type: L
Description: The mineralization is possibly localized along a major ring-fracture system associated with the Cottonwood Creek Volcanic Center.

Type: R
Description: The Hog Ranch property is located in the transitional zone between the Columbia Plateau physiographic province to the north, and the Basin and Range province to the south with a collapsed caldera or failed caldera system possibly present.

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Alterations

Alteration Type: L
Alteration Text: There are two disticnct alteration systems present: a large one associated with the north Hog ranch deposits and a smaller one around the Bell Springs deposit to the south. The northern system is dominated by clay mineralization zoning from near-surface kaolinite to illite at depth. Host rocks are affected by pervasive hydrothermal silicification, opalization, and kaolinization.

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Rocks

Name: Rhyolite
Role: Associated
Description: flows, domes, pyroclasitcs, and extrusives (peralkaline)
Age Type: Associated Rock
Age Young: Miocene

Name: Mixed Clastic/Volcanic Rock
Role: Host
Description: sinter
Age Type: Host Rock
Age in Years: 15.100000+-0.400000
Dating Method: K-Ar
Material Analyzed: whole rock on non-hydrated peralkaline r
Age Young: Middle Miocene

Name: Pyroclastic Rock
Role: Host
Description: explosion breccia
Age Type: Host Rock
Age in Years: 15.100000+-0.400000
Dating Method: K-Ar
Material Analyzed: whole rock on non-hydrated peralkaline r
Age Young: Middle Miocene

Name: Rhyolite
Role: Host
Age Type: Host Rock
Age in Years: 15.100000+-0.400000
Dating Method: K-Ar
Material Analyzed: whole rock on non-hydrated peralkaline r
Age Young: Middle Miocene

Name: Tuff
Role: Host
Description: rhyolitic lapilli
Age Type: Host Rock
Age in Years: 15.100000+-0.400000
Dating Method: K-Ar
Material Analyzed: whole rock on non-hydrated peralkaline r
Age Young: Middle Miocene

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Analytical Data

Not available

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Materials

Ore: Gold
Gangue: Quartz
Gangue: Alunite
Gangue: Sulfur
Gangue: Cinnabar
Gangue: Stibnite
Gangue: Realgar
Gangue: Stibnite
Gangue: Pyrite
Gangue: Clay
Gangue: Chalcedony

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Comments

Comment (Commodity): Ore Materials: free gold, minor auriferous pyrite

Comment (Commodity): Gangue Materials: pyrite, stibnite, realgar, stibnite, cinnabar, native sulfur, alunite, chalcedony, iron oxides, quartz, clay

Comment (Economic Factors): From 1985 to 1992, the mine produced 8.5 million short tons of ore with an average grade of 0.036 ounces per ton. Total production from Hog Ranch from 1986?87 was 80,000 ounces of gold and from 1988?95, 118,045 ounces of gold and 25,400 ounces of silver. In1984 reserves were reported at 2.5 million tons of ore grading 0.085 opt gold. In 1988, Proven and probable reserves were 5.5 million tons of ore grading 0.064 opt Au. with a geologic resource of 20.1 million tons of ore grading 0.029 opt Au. In 1996 Western Mining reported a remaining measured and indicated resource of 1.45 million tonnes at an average grade of 1.13 grams of gold per tonne, plus an additional inferred resource of 0.4 million tonnes at a grade of 1.85 grams of gold per tonne

Comment (Environment): Magmatism associated with continental extension under reducing conditions

Comment (Geology): The Hog Ranch property is located in the transitional zone between the Columbia Plateau physiographic province to the north, and the Basin and Range province to the south. The region exhibits characteristics of both provinces. The Krista pit exhibits features common to a typical disseminated hot-spring Au-Ag deposit which has strong structural control. Gold values are largely found in, and are highest in the more intensely silicified (chalcedonized) rocks. Probable near surface mineralization. Slightly anomalous radioactivity has been reported from petrified wood in late Miocene sedimentary rocks. Uranium occurrences are found along Hog Ranch Creek for several miles.

Comment (Deposit): The mineralization is contained in six orebodies. Ore zones consist of low-grade gold disseminated in flat-lying tabular bodies, with higher grade pods in areas of quartz+ adularia veining. Alteration at the Bell Springs deposit is predominantly silicification of tuffs that contain abundant fine-grained adularia and pyrite. Gold mineralization is related both spatially and temporally to peralkaline silicic volcanism and with a probable ring-fracture system. Opalitic veining occurs. Gold occurs as finely disseminated flecks, and in some places, is associated with pyrite.

Comment (Development): The area underwent exploration for uranium in the 1970s prior to the gold discovery. The Hog Ranch area was staked about 1980, optioned by Noranda about 1984, who, with Ferret Exploration did extensive drilling and exploration on it. In Aug. 1984, Geomex owned a 63% working interest in Hog Ranch and was doing more drilling and metallurgical testing on it. Imperial Metals had acquired an interest in Hog Ranch by Feb, 1986. Western Goldfields and Ferret Exploration acquired the property and were seeking operation permits in March 1986 which were granted, and operations commenced in April, 1986. In August 1986, Orofino Resources acquired a 10% interest in it with other partners Western Goldfields, 50% ; Geomex Minerals, 30%; and Montagu Mining Investments, 10%. Leach pads were being filled in Sept, 1986. In April 1987, Royal Resources Corp bought up all Montagu's stock including its 10% Hog Ranch interest. First pour was in late 1986 with expected production of 50,000 oz Au/year. Western Goldfields increased its interest to 65%. Initial mining was mostly at the Krista pit with continued work to develop ore south of Krista. Feasibility study for the Bell Spring deposit 4 miles SW of the Krista pit was underway with plans to start development on it in 1988. Active mining occurred until 1992 after which gold recovery continued during closure and reclamation until 1996. With higher gold prices in the 2000s, there was renewed exploration interest in the Hog Ranch area, and in 2004-Romarco Minerals Inc. announced that it had begun a Phase II drilling program at the Hog Ranch Project as follow up to its Phase I program, which discovered both high grade gold mineralization that may support underground mining, and a broad zone of significant grade mineralization that is well within open pit mining depths. The best intercepts from Phase 1 were penetrated in drill hole HR-04-3, and consisted of 70 feet (21.3 m) interval averaging 0.152 oz/ton gold (5.23 g/t) that begins approximately 225 feet (69 m) below the surface. Within this 70 foot interval were two 5 foot (1.5m) high grade intervals assaying 0.837 oz/ton gold (28.7 g/t) and 0.502 oz/ton gold (17.2 g/t), respectively. The Phase II program includes drill holes that are designed to extend the mineralization penetrated in HR-04-3, and also holes that will begin testing other high priority targets on the property. The planned drilling program will consist of approximately 4500 feet (1372m) of diamond core drilling in six holes.Of the six planned drill holes, three are to be drilled about midway between the previously-mined Geib and Krista Pits. Two of the holes will attempt to extend the mineralization found in HR-04-3 along strike, and one hole will test for an extension of the mineralization down dip. One of Romarco's primary target areas has always been the Krista Pit, which was the largest deposit mined by Western Hog Ranch Company. Two holes will be drilled under the north and south ends, respectively, of the Krista Pit to test for feeder structures in those areas. In the Geib pit area, one hole will be drilled to test a target below and adjacent to the pit at an interpreted structural intersection. In 2000, Seabridge Gold leased the Hog Ranch property from Platoro and in 2006 was drilling to test deeper parts of the Hog Ranch gold system with the possibility of developing an underground mine on the property.

Comment (Identification): This record is an updated version including duplicate information from M232557, W700443, and W700584, which have been deleted. This record incorporates all information in earlier MRDS record M242957 for the Hog Ranch Mine plus additional updated material.

Comment (Location): UTM is to central portion of the Krista pit, one of several pits at Hog Ranch.

Comment (Workings): The mine was developed by at least 4 open pits: Krista, East, Geib, and Bell Springs, as well as a crushing and heap leach facility and a gold recovery plant.

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References

Reference (Deposit): NBMG Mining District File 314: Numerous Press Clippings

Reference (Deposit): NBMG Spec. Pub MI-1987-1995

Reference (Deposit): Bonham, H.F., 1986, NBMG Map 91

Reference (Deposit): Drossulis, Kim, 1988, Geology of the Hog Ranch Mine, Washoe County, Nevada; Geological Society of Nevada, Special Publication - vol.7, pp.67-77.

Reference (Deposit): Romarco Minerals press release, May 2004.

Reference (Deposit): Jones, R.B., 1984, NBMG Field Examination

Reference (Deposit): Garside, L.J., 1973, Radioactive Mineral Occurrences in Nevada: NBMG Bull 81.

Reference (Deposit): Staff, 1988, Directory of Nevada Mine Operations Active During Calendar Year 1987: Nevada Division of Mine Inspection, 84p.

Reference (Deposit): Western Mining Corp, 1990, Annual Report for Fiscal Year 1989-1990.

Reference (Deposit): Wwestern Mining Corp, 1991, Annual Report For Fiscal Year 1990-1991.

Reference (Deposit): Nevada Division of Minerals, 1994

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): Bussey, Steven D. , 1995, Gold mineralization and associated rhyolitic volcanism at the Hog Ranch Mine, Northwest Nevada:GSN symposium proceedings, Geology and ore deposits of the American Cordillera

Reference (Deposit): Harvey, D.S., Noble, D.C., McKee, E.H., 1986, Hog Ranch Property: in Isochron West, No 47.

Reference (Deposit): Drossulis, Kim, 1988, Geology of the Hog Ranch Mine, Washoe Co., NV: in GSN 1988 Spring Field Trip Guidebook.

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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.