Bald Mountain Mine

Site Name

Primary: Bald Mountain Mine
Secondary: North Area Deposits
Secondary: Pit 1
Secondary: Pit 2
Secondary: Pit 3
Secondary: Pit 5
Secondary: BF Claim Group
Secondary: One-Five deposit
Secondary: Two-Three deposit

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Commodity

Primary: Gold
Primary: Silver
Tertiary: Zinc
Tertiary: Arsenic
Tertiary: Antimony
Tertiary: Mercury
Tertiary: Bismuth
Tertiary: Tellurium
Tertiary: Copper

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Location

State: Nevada
County: White Pine
District: Bald Mountain 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: Ely BLM district

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Holdings

Not available

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Workings

Not available

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Ownership

Owner Name: Placer Dome U. S., Inc.
Info Year: 2004

Owner Name: Barrick
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: 1983
Discovery Year: 1977
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: Distal disseminated Ag-Au

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Orebody

Form: pipe-like to tabular

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Structure

Type: R
Description: The Bald Mountain district is located in an area of thinned crust along the eastern side of the Late Proterozoic rift that split the North American craton. It is also in the west-central portion of the Late Devonian-Early Mississippian Antler foreland basin, and near the eastern edge of deformation related to the late Paleozoic Humboldt orogeny. To the west of the Bald Mountain district, geologic interpretations are dominated by recognition of Paleozoic deformation, whereas to the east, interpretations emphasize Mesozoic contraction and plutonism and Tertiary extension.

Type: L
Description: The Bald Mountain district is disrupted by structures that range in age from Jurassic to Quaternary faults that cut alluvial fans. Neogene extensional faults that in part reactivated older structures dominate the present-day topography. High-angle normal faults bound the north- to northeast-trending basins that characterize the area and form a series of horsts and grabens. The dominant structural trend is N45W, but there are NE-, N-S, and E-W-trending structures as well. Intense pre- and post-mineral faulting at Bald Mountain has resulted in a complex structural setting, dominantly controlled by intersecting NW and NNE trending deep crustal features

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Alterations

Alteration Type: L
Alteration Text: Alteration consists predominantly of silicification, argillization, and potassic alteration. The main alteration feature at Bald Mountain is the large halo of silicification and strong argillization. Potassic alteration is recognized at depth. In the North area deposits, the sedimentary rocks are variably hornfelsed and were locally pervasively argillized. Siliciclastic rocks are decalcified within ore zones with minor silicification adjacent to ore zones. Pervasive secondary iron oxides resulted from the oxidation of marcasite and pyrite in the host rocks. Higher grade ore is indicated by chocolate-brown goethite.

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Rocks

Role: Associated
Age Type: Associated Rock Unit
Age in Years: 159.000000+-
Age Young: Late Jurassic

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

Name: Limestone
Role: Host
Description: dark gray
Age Type: Host Rock
Age Young: Late Cambrian

Name: Shale
Role: Host
Description: calcareous
Age Type: Host Rock
Age Young: Middle Cambrian

Name: Shale
Role: Host
Description: calcareous
Age Type: Host Rock
Age Young: Late Cambrian

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Analytical Data

Not available

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Materials

Ore: Gold
Gangue: Quartz
Gangue: Pyrite
Gangue: Marcasite

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Comments

Comment (Deposit): Intense pre- and post-mineral faulting at Bald Mountain has resulted in a complex structural setting, dominantly controlled by intersecting NW and NNE trending deep crustal features. Gold deposits are localized and controlled by these structures. The host rocks are calcareous shales and dark gray limestones which weather to iron-oxide stained red-brown-maroon and tan colors. The North area deposits occur along a major NE-trending structure with a strike length of 7500 feet. The One-Five deposit occurs in the southwest part of the mine area and is hosted by Cambrian Dunderburg Shale. The Two-Three deposit is in the northeast mine area and is hosted by middle Cambrian Secret Canyon Shale. Gold mineralization occurs along steep N10E to N10 W normal faults, along N30-50 E normal and reverse faults, and along N30-45W normal faults. The intersections of these major structures localize higher grade ore shoots. The 1-5 area orebodies are sediment-hosted, structure-controlled deposits, not spatially related to the porphyry bodies.

Comment (Development): Placer Dome began exploration on Bald Mountain property in 1977 and the North Area, 1-5 deposits were among the earliest discoveries in the first year of exploration. In 1983, a 2 month, $1.96 million heap leach test produced 3500 ounces of gold from 66,000 short tons of ore. In 1985, test mining and heap leach operations were conducted, a final feasibility decision was made, and the permitting process was completed. The Bald Mountain Mine was converted from pilot scale to full scale production in 1986. Stage III development of the Top orebody commenced in mid-1987 with a third mine shift required to handle increased mine production. Also in 1987, the leach pad was expanded by 180,000 square feet and 3 process solution ponds were lined with artificial membrane material to contain gold-bearing solutions. In 1988, the Top orebody provided most of the heap leach feed, while the RBM deposit was placed into production late in the year. Also in 1988, 5 additional carbon columns were installed and new leach pad construction added 680,000 square feet of leaching area. In 1998, the Mooney Basin Project in the former Alligator Ridge mine area was approved as a satellite operation to Bald Mountain Mine. In 2006, Barrick Gold Corp. acquired the Bald Mountain Mine properties through its acquisition of Placer Dome.

Comment (Identification): The Bald Mountain District deposits under Placer Dome?s control number more than 40 satellitic orebodies. The earlier record #M233723 lumped all the Bald Mountain deposits together over many square miles. This new record covers the northwest area Bald Mountain Mine pits, Pit 1, Pit 2, Pit 3, and Pit 5;. Other Bald Mountain Mine satellite deposits are each covered by separate records. This record incorporates all material pertinent to these pits from the earlier record #M233723 as well as additional material. Bald Mountain Mine and Little Bald Mountain Mine are different properties.

Comment (Location): The Bald Mountain Mining District lies within the Southern Ruby Mountains. UTM is to the central area of Nos. 1-5 pits described by this record. The entire Bald Mountain Mine area covers approximately 4150 claims within the Bald Mountain Mining District. The land position is 48 kilometres long north to south by 8 kilometres wide east to west and encompasses many satellitic orebodies and deposits.

Comment (Workings): Production has come from several open pits in the North mine area.

Comment (Environment): The Bald Mountain deposits are interpreted as forming in a dilational zone along a west- to northwest strike-slip fault during Jurassic compression, and at depths of 3-6 km.

Comment (Economic Factors): Through 1995, Pits Nos. 1-5 had produced 5.6 millon tons of oxide ore grading 0.063 opt gold. From 1999 through 2003, all Placer Dome?s Bald Mountain deposits produced 617,266 ounces of gold from more than 20 million tonnes of ore. Royal Gold holds a 1.75% net smelter return royalty (?NSR?) that covers a portion of the Bald Mountain mine. Placer Dome reported that as of December 31, 2002, at a $300 gold price, the proven and probable reserves related to Royal Gold?s royalty include 9.2 million tons (8.3 million tonnes) of ore, with an average grade of 0.039 ounces per ton (?opt?) (1.34 gpt), containing approximately 363,000 ounces of gold. This compares to proven and probable reserves, at December 31, 2001, at a $275 gold price, of 7.7 million tons (7.0 million tonnes) of ore, with an average grade of 0.030 opt (1.03 gpt), containing approximately 232,000 ounces of gold. In addition to the proven and probable reserves, the operator reports that the Bald Mountain property contains approximately 8.3 million tons (7.6 million tonnes) of additional mineralized material, at an average grade of 0.047 opt (1.61 gpt) of gold. This compares to additional mineralization, as of December 31, 2001, of approximately 9.1 million tons (8.3 million tonnes), at an average grade of 0.076 opt (2.61 gpt) of gold.Proven and probable mineral reserves for the entire Bald Mountain property, including all satellitic deposits as of December 31, 2003 are estimated at approximately 676,000 ounces of gold (332,000 proven and 344,000 probable).

Comment (Geology): Geology Sedimentary rocks exposed in the Bald Mountain Mining District range in age from Cambrian to Tertiary. This generally conformable assemblage of limestone and dolomite, with lesser amounts of siltstone and shale, has been intruded by Jurassic plutonic rocks. Intense pre- and post-mineral faulting at Bald Mountain has resulted in a complex structural setting, dominantly controlled by intersecting NW and NNE trending deep crustal features. Gold deposits are localized and controlled by these structures. The Top deposit is the largest known mineral resource in the district. Gold mineralization is hosted in quartz feldspar porphyry and dolomites along the margin of the Bald Mountain stock. Higher-grade gold mineralization is controlled by northeast and northwest trending normal faults. The ore body forms a pipe-like shape, which rakes to the northeast along the plunge of the intersection of the major NW and NNE structural zones. The Bald Mountain Mining District contains more than 40 documented gold occurrences. At present, various operators have mined fourteen of these deposits. Other deposits included in the mine plan are the Rat, RBM, and North Pits on the western flank of Big Bald Mountain; the Top and Sage Flats on the east flank of Big Bald Mountain; the Poker Flats, Horseshoe, Bida, Saga, Galaxy, and Winrock deposits, which are located on the eastern flank of Little Bald Mountain and along the margins of the Mooney Basin. When mined, these deposits will be processed at a current or future processing facility. Host rock and style of gold mineralization varies through out the district. The Big Bald Mountain area deposits are hosted in shale, limestone, dolomite or intrusive and may locally contain high grades. The Mooney Basin area deposits and Alligator Ridge area deposits are hosted in the Pilot Shale and are generally lower grade. The Mooney Basin area has numerous oxide deposits under evaluation. Gold in the Bald Mountain Mining District generally occurs as disseminated micron-sized particles. Rare visible gold is seen in the eastern portion of the Top deposit. Presently, all ores that have been mined are oxidized, but numerous occurrences of mineralized carbonaceous material are present within the land package The North deposits have low to non-existent base metal signatures with higher Hg, As, and Sb values. Sedimentary rocks exposed in the Bald Mountain District range in age from Cambrian to Tertiary. This generally conformable assemblage of limestone and dolomite, with lesser amounts of siltstone and shale, has been intruded by Jurassic plutonic rocks. Previous studies concluded that the Devonian-Mississippian deposits are Carlin-type and the Bald Mountain deposits pluton-related. However, the later stages of mineralization and more distal deposits at Bald Mountain exhibit a number of characteristics, such as gold-bearing arsenian pyrite, marcasite, or arsenopyrite, high Au/Ag ratios, argillic alteration, or sulfidation of igneous dikes, that are suggestive of Carlin-type min- eralization. Despite these characteristics, petrographic, geo- chemical, and isotopic work on these stages and deposits confirm that they too are pluton-related and that there is no evidence of a Carlin-type overprint at Bald Mountain.

Comment (Commodity): Ore Materials: gold

Comment (Commodity): Gangue Materials: quartz, pyrite,marcasite, iron oxides

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References

Reference (Deposit): The Geological Society of Nevada 1996 Spring Field trip, Geology and Gold Deposits of Eastern Nevada, GSN Special Publication No. 23.

Reference (Deposit): Hose, Blake, and Smith, 1976, Geology and Mineral Resources of White Pine County, Nevada, NBMG Bulletin 85.

Reference (Deposit): Hill, J. M., 1916, Notes on some Mining Districts in Eastern Nevada, USGS Bull. 648, p. 152-161.

Reference (Deposit): Dean, D. A., Benedetto, K. M. F., Durgin, D. C., 1991, Part Two: Ely - Bald Mountain - Ely Road Log, in Buffa, R. and Coyner, A., eds., Geology and Ore Deposits of the Great Basin - Field Trip Guidebook Compendium, The Geological Society of Nevada, Reno, p. 136-162.

Reference (Deposit): Lowe, N. T., Raney, R. G., and Norberg, J. R., Principal Deposits of Strategic and Critical Minerals in Nevada, USBM Information Circular 9035, p. 75.

Reference (Deposit): A Study of Active U. S. Gold Mines, July, 1986, Metals Economics Group, Boulder, Co, p. 288-291.

Reference (Deposit): Placer Dome Inc., Annual Report for 1987.

Reference (Deposit): Placer Dome Inc., Annual Report for 1988.

Reference (Deposit): Placer Dome Inc., Annual Report for 1989.

Reference (Deposit): Placer Dome Inc., Annual Report for 1990.

Reference (Deposit): Bonham, H., Bentz, J., and Smith, P., 1981, Field Examination, June 28, 1981.

Reference (Deposit): NBMG, 1982, Open File Report 82-9.

Reference (Deposit): Pay Dirt, Oct, 1982.

Reference (Deposit): Nevada Mining Association Bulletin, 1983.

Reference (Deposit): Royal Gold Inc. press release, March 2003.

Reference (Deposit): Adella Harding, Elko Daily Free Press Mining Quarterly, Fall 2002.

Reference (Deposit): Nutt, C.J., Hofstra, A.H., Hart, K.S., and Mortensen, J.K., 2000, Structural setting and genesis of gold deposits in the Bald Mountain-Alligator Ridge area, east-central Nevada, in Cluer, J.K., Price, J.G., Struhsacker, E.M., Hardyman, R.F., and Morris, C.L., eds., Geology and Ore Deposits 2000: The Great Basin and Beyond: Geological Society of Nevada Symposium Proceedings, May 15-18, 2000, p. 513-537.

Reference (Deposit): Hitchborn and others, 1996, Geology and Gold Deposits of the Bald Mountain Mining District, White Pine County, Nevada, in Geology and Ore Deposits of the American Cordillera Symposium Proceedings, eds. A. Coyner and P. Fahey.

Reference (Deposit): The Geological Society of Nevada 1996 Spring Field trip, Geology and Gold Deposits of Eastern Nevada, GSN Special Publication No. 23.

Reference (Deposit): BLM, 2004, Bald Mountain Mine Exploration Program Programmatic Environmental Assessment NV040-04-023, Case File # N78825.

Reference (Deposit): Division of Mine Inspection, 1983, Directory of Nevada Mining Operations Active During Calendar Year 1983.

Reference (Deposit): Jones and Papke, 1984, Active Mines and Oil Fields in Nevada - 1983, NBMG Map M84.

Reference (Deposit): NBMG, 1994, MI-1993

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. NBMG MI-2002

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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.