Bald Mountain Mine

Producer in White Pine county in Nevada, United States with commodities Gold, Silver, Copper, Zinc, Arsenic, Antimony, Mercury, Bismuth, Tellurium

Sections on this page

Identification information
Geographic coordinates
Site location context
Geographic areas
Public Land Survey System information
Commodities
Materials information
Alteration
Mineral occurrence model information
Host and associated rocks
Nearby scientific data
Geologic structures
Ore body information
Controls for ore emplacement
Economic information about the deposit and operations
Mining district
Land status
Ownership information
Bibliographic references
General comments
Reporter information

Geologic information

Identification information

Deposit ID	10310370
MRDS ID	M233723
Record type	Site
Current site name	Bald Mountain Mine
Alternate or previous names	North Area Deposits, Pit 1, Pit 2, Pit 3, Pit 5, BF Claim Group, One-Five deposit, Two-Three deposit
Related records	10045868, 10310447, 10310551

Comments on the site 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.

Geographic coordinates

Geographic coordinates:	-115.59589, 39.96659 (WGS84)
Elevation	2180
Relative position	The Bald Mountain Mine is located approximately 110 kilometers (60 miles) northwest of Ely, Nevada and about 110 kilometers (60 miles) south-southeast of Elko, Nevada.

Site location context

Political divisions (FIPS codes)

White Pine(county)

Nevada(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Big Bald Mountain(quadrangle 1:24,000 scale)

Newark Lake(quadrangle 1:100,000 scale)

Ely(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

South Fork Humboldt(hydrologic unit)

Humboldt(hydrologic accounting unit)

Black Rock Desert-Humboldt(hydrologic subregion)

Great Basin(hydrologic region)

Federal lands

Bureau of Land Management(Bureau of Land Management NV)

Bureau of Land Management NV BLM(Type of land area)

BLM(Federal land areas administered by BLM)

Geographic areas

Country	State	County
United States	Nevada	White Pine

Public Land Survey System information

Meridian	Township	Range	Section	Fraction	State
Mount Diablo	024N	057E	7, 8		Nevada

Comments on the location information

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.

Commodities

Commodity	Importance
Gold	Primary
Silver	Primary
Copper	Tertiary
Zinc Critical	Tertiary
Arsenic Critical	Tertiary
Antimony Critical	Tertiary
Mercury	Tertiary
Bismuth Critical	Tertiary
Tellurium Critical	Tertiary

Comments on the commodity information

Ore Materials: gold
Gangue Materials: quartz, pyrite,marcasite, iron oxides

Materials information

Materials	Type of material
Gold	Ore
Quartz	Gangue
Pyrite	Gangue
Marcasite	Gangue

Alteration

(Local) 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.

Mineral occurrence model information

Model code	75
USGS model code	19c
Deposit model name	Distal disseminated Ag-Au
Mark3 model number	18

Host and associated rocks

Host or associated

Host

Rock type

Sedimentary Rock > Clastic Sedimentary Rock > Shale

Rock type qualifier

calcareous

Rock unit name

Dunderberg Shale

Stratigraphic age (youngest)	Late Cambrian

Host or associated

Host

Rock type

Sedimentary Rock > Clastic Sedimentary Rock > Shale

Rock type qualifier

calcareous

Rock unit name

Secret Canyon Shale

Stratigraphic age (youngest)	Middle Cambrian

Host or associated

Host

Rock type

Sedimentary Rock > Carbonate > Limestone

Rock type qualifier

dark gray

Rock unit name

Carlin member, Windfall Formation

Stratigraphic age (youngest)	Late Cambrian

Host or associated Host

Rock type Plutonic Rock > Porphyry

Rock type qualifier quartz feldspar
Host or associated Host

Rock type Sedimentary Rock > Carbonate > Dolomite
Host or associated Associated

Rock type Plutonic Rock > Granitoid > Granite

Stratigraphic age (youngest) Tertiary
Host or associated Associated

Rock type

Rock unit name Bald Mountain Stock

Stratigraphic age (youngest) Late Jurassic

Chronological age 159

Host or associated	Host
Rock type	Plutonic Rock > Porphyry
Rock type qualifier	quartz feldspar

Host or associated	Host
Rock type	Sedimentary Rock > Carbonate > Dolomite

Nearby scientific data

(1)	-115.59589, 39.96659	ListMap

Economic information

Geologic structures

Type of structure	Regional
Structure 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 of structure	Local
Structure 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

Ore body information

General form pipe-like to tabular

General form	pipe-like to tabular

Controls for ore emplacement

Mineralization is strongly structurally controlled. Gold mineralization occurs along steep N10E to N10 W normal faults, along N30-50 E normal and reverse faults, and alongN30-45W normal faults. The intersections of these major structures localize higher grade ore shoots.The dominant structural trend is N45W, but there are NE-, N-S, and E-W-trending structures as well. The E-W structures show the youngest period of movement, some of which is post-ore.

Comments on the geologic information

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.

Economic information about the deposit and operations

Operation type	Surface
Development status	Producer
Commodity type	Metallic
Deposit size	Medium
Significant	Yes
Discovery year	1977
Year of first production	1983
Production years	1983; 1985 - present 2006

Mining district

District name	Bald Mountain District

Land status

Ownership category	BLM Administrative Area
Area name	Ely BLM district

Ownership information

Type Owner-Operator

Owner Placer Dome U. S., Inc.

Year 2004
Type Owner-Operator

Owner Barrick

Year 2006

Type	Owner-Operator
Owner	Placer Dome U. S., Inc.
Year	2004

Type	Owner-Operator
Owner	Barrick
Year	2006

Comments on the workings information

Production has come from several open pits in the North mine area.

Comments on other 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).

Comments on 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.

Comments on the environmental information

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.

Reference information

Bibliographic references

Deposit

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

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

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

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

Placer Dome Inc., Annual Report for 1987.
Deposit

Placer Dome Inc., Annual Report for 1988.
Deposit

Placer Dome Inc., Annual Report for 1989.
Deposit

Placer Dome Inc., Annual Report for 1990.
Deposit

Bonham, H., Bentz, J., and Smith, P., 1981, Field Examination, June 28, 1981.
Deposit

NBMG, 1982, Open File Report 82-9.
Deposit

Pay Dirt, Oct, 1982.
Deposit

Nevada Mining Association Bulletin, 1983.
Deposit

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

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

NBMG, 1994, MI-1993
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
Deposit

Royal Gold Inc. press release, March 2003.
Deposit

Adella Harding, Elko Daily Free Press Mining Quarterly, Fall 2002.
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.
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.
Deposit

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

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

General comments

Subject category	Comment text
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.

Subject category

Comment text

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.

Reporter information

Type	Date	Name	Affiliation	Comment
Reporter	01-NOV-2004	LaPointe, D. D.	Nevada Bureau of Mines and Geology
Editor	01-SEP-2007	Schruben, Paul G.	U.S. Geological Survey	Converted from S&A FileMaker format to Oracle. Edit checks on rocks, units, and ages with Geolex search, and other fields.

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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