Sleeper Mine

Producer in Humboldt county in Nevada, United States with commodities Gold, Silver, Potassium, Sulfur, Arsenic, Selenium, Antimony, Mercury, Thallium, Molybdenum, Barium-Barite, Bismuth, Copper, Lead, Tellurium, Zinc, Cobalt, Nickel

Geologic information

Identification information

Deposit ID 10310319
MRDS ID W700408
Record type Site
Current site name Sleeper Mine
Alternate or previous names Sleeper Pit, Wood Pit, West Wood, Bedrock Casino, Northeast areas

Comments on the site identification

  • This record incorporates all material from earlier records for the same deposit: MRDS # W700408,W700596, M242534, and M242951, which should be deleted from the file.

Geographic coordinates

Geographic coordinates: -118.0524, 41.3338 (WGS84)
Elevation 1300
Relative position The mine is located about 45 km NW of Winnemucca.
(click for info)

Geographic areas

Country State County
United States Nevada Humboldt

Public Land Survey System information

Meridian Township Range Section Fraction State
Mount Diablo 040N 035E 21 Nevada

Comments on the location information

  • The mine is located in Desert Valley on the NW Flank of the Slumbering Hills.

Commodities

Commodity Importance
Gold Primary
Silver Primary
Potassium Tertiary
Sulfur Tertiary
Arsenic Tertiary
Selenium Tertiary
Antimony Tertiary
Mercury Tertiary
Thallium Tertiary
Molybdenum Tertiary
Barium-Barite Tertiary
Bismuth Tertiary
Copper Tertiary
Lead Tertiary
Tellurium Tertiary
Zinc Tertiary
Cobalt Tertiary
Nickel Tertiary

Comments on the commodity information

  • Ore Materials: native gold
  • Gangue Materials: quartz, adularia, stibnite, pyrite, marcasite, opal, cristobalite, sericite, alunite, kaolinite, smectite, barite, illite, jarosite.

Materials information

Materials Type of material
Gold Ore
Quartz Gangue
Adularia Gangue
Stibnite Gangue
Pyrite Gangue
Marcasite Gangue
Opal Gangue
Cristobalite Gangue
Sericite Gangue
Alunite Gangue
Kaolinite Gangue
Barite Gangue
Illite Gangue
Jarosite Gangue

Alteration

  • (Local) Alteration of rhyolitic host rock consists predominantly of silicification, argillic alteration, acid leaching, and supergene alteration. Replacement and open-space filling by silica minerals are the most prominent and diagnostic alteration styles at Sleeper. Early silicification, accompanied by pyrite, resulted in pervasive replacement of plagioclase phenocrysts and groundmass by opaline silica. Alunite occurs in some early silicified rocks, but possibly was a later addition. Silicification of several types accompanied ore stages. Late-stage silicification in the form of opal is controlled by post-ore faults and fractures and is barren of gold. This late opal typically contains abundant light-colored alunite, kaolinite, or jarosite. Small amounts of native sulfur are enclosed in the late silica. Hypogene argillic alteration occurs peripheral to zones of early silicification; commonly there is a transition zone from 3 to 50 m wide of clay-altered plagioclase in silicified groundmass. The broad argillized zones are barren of Ag and Au, and contain little sulfide and no silica veinlets. Feldspar phenocrysts and aphanitic groundmass in argillized zones commonly are altered to clay minerals, most commonly kaolinite, smectite, and illite. Plagiocalse phenocrysts have been replaced by fine-grained clay minerals and alunite. Sanidine is locally altered to sericite or kaolinite. Groundmass is generally altered to very fine grained silica-clay mixtures. Thoroughly acid-leached rocks with sponge-like texture of more than 90% silica occur in local zones along post-ore faults. Subsequently, opal, alunite, and jarosite were deposited in the porous rocks. The prominent red coloration of upper pit walls reflects supergene destruction of sulfides and local redistribution of iron into fractures. Pyritic tuffs have been oxidized to tan alunite+jarosite+limonite-bearing mixtures. Feldspars are altered to white clays along open fractures and voids later filled by phases of unusual composition, some rich in Cl (as NaCl and AgCl), and various combinations of Al, Mn, and Co As oxides or sulfates. Propylitically altered tuffaceous sediments, andesitic lava flows, and metasedimentary basement rocks underlie the rhyolitic host rock.

Analytical data

Result All rocks in the pit are enriched in K and S, and depleted in Ca and Na
Result Al commonly is mobile. Ore zones are enriched in As and Se and are sporadically enriched in Sb, Hg, Tl, and Mo
Result Concentrations of Ba, Bi, Cu, Pb, Te, and Zn are generally low. NBMG sample 3306, a dump grab of silicified, argillized intermediate volcanic material, contains 3% Fe, 0.15% Mg, 0.05% Ca, 0.3% Ti, 30 ppm Mn, 5 ppm Ag, 5 ppm As, 30 ppm B, 700 ppm Ba, 30 ppm Cr, 150 ppm Cu, 20 ppm La, 30 ppm Mo, 10 ppm Pb, 300 ppm Sb, 7 ppm Sc, 100 ppm Sr, 70 ppm V, 10 ppm Y, 150 ppm Zr, and by AA analysis, 0.6 ppm Au. Sample 3307 of altered, sulfide-bearing dump volcanics contains 1% Fe, 0.07% Mg, 0.05% Ca, 0.3% Ti, 30 ppm Mn, 10 ppm Ag, 20 ppm B 700 ppm Ba, 1 ppm Be, 50 ppm Cr, 100 ppm Cu, 5 ppm Pb, 150 ppm Sb, 5 ppm Sc, 7 ppm V, 100 ppm Zr, and by AA analysis, 0.2 ppm Au.

Mineral occurrence model information

Model code 150
USGS model code 25c
Deposit model name Epithermal vein, Comstock
Mark3 model number 16

Host and associated rocks

  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Felsic Volcanic Rock > Rhyolite
    Rock type qualifier porphyry
    Stratigraphic age (youngest) Miocene
  • Host or associated Host
    Rock type Plutonic Rock > Porphyry
    Rock type qualifier Rhyolite
    Stratigraphic age (youngest) Miocene
  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Intermediate Volcanic Rock > Andesite
    Stratigraphic age (youngest) Miocene
  • Host or associated Host
    Rock type Metamorphic Rock > Phyllite
    Rock unit name Auld Lang Syne Group
    Stratigraphic age (youngest) Early Jurassic
    Stratigraphic age (oldest) Late Triassic
  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Slate
    Rock unit name Auld Lang Syne Group
    Stratigraphic age (youngest) Early Jurassic
    Stratigraphic age (oldest) Late Triassic
  • Host or associated Host
    Rock type Metamorphic Rock > Metasedimentary Rock > Quartzite
    Rock unit name Auld Lang Syne Group
    Stratigraphic age (youngest) Early Jurassic
    Stratigraphic age (oldest) Late Triassic

Nearby scientific data

(1) -118.0524, 41.3338

Geologic structures

Type Description Terms
Regional In the northern Slumbering Hills, Triassic sedimentary rocks are weakly folded and form a N20E-trending monocline that dips 45 east.
Local The Sleeper Deposit occurs within a N20E-striking range front fault zone that dips 45-85 and terminates the NW side of the range. This fault zone hosted extensive hydrothermal alteration and mineralization and localized the Sleeper Gold Deposit. A normal fault which strikes N50W and dips 72 south intersects the range front fault zone in the vicinity of the Sleeper Deposit.

Ore body information

  • General form tabular to disseminated to irregular
    Strike N-S
    Dip 60-70 W
    Depth to top 50M
    Length 1200M
  • Strike NNE
    Dip STEEP W
    Thickness 100M
    Width 100M
    Length 400M
  • Thickness 9.14M

Controls for ore emplacement

  • Brittle rocks (mainly rhyolite porphyry) were required for deposition of gold in open tension fractures and as stockwork veins and hydrothermal breccias.

Comments on the geologic information

  • Nash, et al. (1991) do not classify Sleeper as a hot springs deposit because ore spans a vertical distance of >500m. However, the setting was shallow (probably 50-500m depth).

Economic information

Economic information about the deposit and operations

Operation type Surface
Development status Producer
Commodity type Both metallic and non-metallic
Deposit size Medium
Significant Yes
Discovery year 1982
Discoverer John Wood, an AMAX geologist, made the discovery and staked the claims.
Discovery method Geochemical And Geophysical Anomaly
Year of first production 1986
Year of last production 1996
Production years 1986 - 1996
Milling method Heap Leach-Agglomerate-Carbon Column-Electrowin

Mining district

District name Awakening District
District name Amos District
District name Slumbering Hills

Land status

Ownership category BLM Administrative Area
Area name Winnemucca BLM District

Ownership information

  • Type Owner
    Owner X-Cal Resources
    Interest 100
    Home office Canada
    Year 1997
    First year 1997
  • Type Owner-Operator
    Owner Sleeper Joint Venture partners, New Sleeper Gold Corporation (TSX-V: NWS)
    Interest 50
    Year 2004
  • Type Operator
    Owner Amax Gold, Inc.
  • Type Owner-Operator
    Owner Sleeper Joint Venture partners, X-Cal Resources Ltd.
    Interest 50
    Year 2004
  • Type Operator
    Owner Nevada Gold Mining, Inc.
    First year 1988
  • Type Owner
    Owner X-Cal Resources
    Interest 50
    Home office Canada
    Year 1996
    First year 1996
    Last year 1997
  • Type Owner
    Owner Amax Inc. (Nevada Gold Mining Inc., a wholly-owned subsidiary of Amax)
    First year 1988
  • Type Owner
    Owner Amax Gold, Inc.
    Interest 50
    Home office Colorado
    Year 1996
    First year 1996
    Last year 1997
  • Type Owner
    Owner Owner listed as Amax, Inc.
    First year 1987
  • Type Owner
    Owner Amax Gold, Inc.
    ID 2670255
    Interest 100
    Home office Colorado
    Year 1996
    First year 1990
    Last year 1996
  • Type Operator
    Owner Nevada Gold Mining, Inc. (100% sub of Amax Gold Inc.)
    Home office Nevada
    Year 1996
    First year 1991
    Last year 1996

Production statistics

  • Year 1986
    Description 168265 Mt Milled 4124000 Grams Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 4,124,000g
  • Year 1987
    Description 267067 Mt Milled, 910,194 Mt Leached 4936000 Grams Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 4,936,000g
  • Year 1988
    Description 344449 Mt Milled, 4,401,190 Mt Leached 7167000 Grams Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 7,167,000g
  • Year 1989
    Description 492735 Mt Milled, 4,777,315 Mt Leached 7969000 Grams Au
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major Gold Gold 7,969,000g
  • Year 1991
    Description Silver Production 9003308 Grams
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Trace Silver Silver 9,003,308g
    Primary Gold Gold 5,702,700g
  • Year 1994
    Description Gold Production (Hl Gold-36,162 Tr Oz) 106912 Tr Oz
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Primary metal recovered Gold Gold 3mt
    Primary metal recovered Silver Silver 4mt
  • Year 1994
    Description Ore Heap Leadhed @ 0.016 Tr Oz/St 5012600 St Ore
  • Year 1994
    Description Ore Milled @ 0.11 Tr Oz/St 802534 St Ore
  • Year 1995
    Description Gold Production (Hl Gold-27,331 Tr Oz) 82062 Tr Oz
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Primary metal recovered Gold Gold 3mt
    Primary Silver Silver 3,069,727g
  • Year 1995
    Description Ore Heap Leached @ 0.018 Tr Oz/St 2779000 St Ore
  • Year 1995
    Description Ore Milled @ 0.095 Tr Oz/St 857284 St Ore
  • Year 1996
    Description Gold Production (Hl Gold-12,356 Tr Oz) 38199 Tr Oz
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Primary metal recovered Gold Gold 1mt
    Primary metal recovered Silver Silver 1mt
  • Year 1996
    Description Ore Heap Leached @ 0.02 Tr Oz/St 454100 St Ore
  • Year 1996
    Description Ore Milled @ 0.069 Tr Oz/St 570975 St Ore

Reserves and resources

  • Type In-situ
    Estimate year 1985
    Total resources 1,904,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 3.67 g/mt Gold Major 1985
    Silver Ag 20.612 g/mt Silver Major 1985
  • Type In-situ
    Estimate year 1985
    Commodity Subtype Grade units Group Importance Year
    Gold Au 6.211 g/mt Gold Major 1985
    Silver Ag 22.588 g/mt Silver Minor 1985
  • Type Milling
    Estimate year 1986
    Commodity Subtype Grade units Group Importance Year
    Gold Au 7.087 g/mt Gold Major 1986
  • Type Leaching
    Estimate year 1986
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.847 g/mt Gold Major 1986
  • Type In-situ
    Estimate year 1986
    Commodity Subtype Grade units Group Importance Year
    Gold Au 3.67 g/mt Gold Major 1986
  • Type In-situ
    Estimate year 1987
    Commodity Subtype Grade units Group Importance Year
    Gold Au 3.67 g/mt Gold Major 1987
    Silver Ag 20.612 g/mt Silver Major 1987
  • Type Milling
    Estimate year 1987
    Commodity Subtype Grade units Group Importance Year
    Gold Au 10.616 g/mt Gold Major 1987
  • Type Leaching
    Estimate year 1987
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.592 g/mt Gold Major 1987
  • Type Milling
    Estimate year 1988
    Commodity Subtype Grade units Group Importance Year
    Gold Au 8.95 g/mt Gold Major 1988
  • Type Leaching
    Estimate year 1988
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.592 g/mt Gold Major 1988
  • Type Milling
    Estimate year 1989
    Commodity Subtype Grade units Group Importance Year
    Gold Au 7.369 g/mt Gold Major 1989
  • Type Leaching
    Estimate year 1989
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.592 g/mt Gold Major 1989
  • Type Milling
    Estimate year 1990
    Commodity Subtype Grade units Group Importance Year
    Gold Au 5.308 g/mt Gold Major 1990
  • Type Leaching
    Estimate year 1990
    Commodity Subtype Grade units Group Importance Year
    Gold Au 0.621 g/mt Gold Major 1990
  • Type In-situ
    Estimate year 1996
    Demonstrated 787,000mt ore
    Commodity Subtype Grade units Group Importance Year
    Gold Au 1.89 g/mt Gold Major 1996

Workings at the site

  • Type of workings Surface
    Overall length 2400M
    Overall width 500M
  • Type of workings Surface
    Area 133HA
    Field Value
    MAS Development Schedule # 1
    Mining Record # 1
    Status of Mining Method ACTUAL
    Mining Method OPEN PIT
    Swell Factor .2
    Percent Waste Rock .5
    Avg. Overburden Thickness 0
    Hardness of Ore M-HARD ROCKS
    Avg. Bench Height (meters) 7.6
    Capacity 20270
    Capacity Units MT ORE/DAY
    Unit Production Cost 2.24
    Units of Production $/MT ORE
    Operating Days per Year 260
    Operating Shifts per Day 2
    Year of Information 1990

Comments on the workings information

  • Historic workings in the Sleeper mine area, dating probably from about the 1930's, included two shafts, 3 adits, and 17 prospect pits within a 2 km radius of the current Sleeper mine. The current mine workings include open pits, heap leach pads, mill, and recovery facilities as well as peripheral drill roads, drill holes, and surface prospecting. The Sleeper pit was begun in 1986, followed in 1987 by the Wood pit immediately to the south. In 1989 the two pits were joined to make one pit >2.4 km long and 0.5 km wide, but the earlier names were retained: Sleeper for the northern part and Wood for the southern part. Initial milling rate was 500 tpd but was expanded in 1989 to 1500 tpd at an average head grade of 0.48 opt Au. An additional 17,000 tpd were crushed and stacked for heap leaching. Cash production cost in 1988 was $103/oz. High-grade ore contains Au coarse enough for gravity recovery, a circuit that accounts for 20% of Au production. Overflow is cyanide-leached with high recovery despite some ore with high sulfide content. Milling is not optimized for Ag, but approx. equal amounts of Ag and Au are recovered. Mine employed up to 100 persons, and mine life was initially expected to be about ten years.

Comments on other economic factors

  • The Sleeper open pit mine was among Nevada's most high grade gold deposits. The Sleeper deposit produced 1,685,500 ounces of gold and 2,334,400 ounces of silver between 1986 and 1996, at average cash costs of 158 dollars per ounce of gold. Annual production averaged 200,000 ounces per year from 1986 to 1992 but was declining at that time due to lower grades at depth. In 1994, the deposit was said to contain 1.5 million ounces of recoverable gold in vein ores as well as 1 million ounces in lower grade disseminated ore. In 1997 the total measured, indicated, and inferred geologic resource at Sleeper was reported to be 2.27 million ounces of gold. In 1998 the estimated in-ground mineral inventory was 182 million tons of material grading 0.043 opt gold. In fall 2006, X-Cal Resources Ltd. reported inferred resources of 150,000 tons of material grading 0.363 ounces of gold per ton for the Sleeper project.

Comments on development

  • During a 1982 aerial reconnaissance program conducted by AMAX Exploration, Inc., geologist John Wood spotted an iron-oxide stained scarp which was the focus of follow-up mapping and sampling that indicated a large continuous geochemical anomaly in a zone 50-300m wide and more than 1000m long that was bounded on the east by a large normal fault and was covered by alluvium to the west. Within this zone 65 rock chip samples averaged about 0.2 ppm Au, 200 ppm As, and 100 ppm Sb with anomalous metals such as Ag, Hg, Tl, and Ba. This geochemical anomaly was characteristic of epithermal precious metal mineralization. Vegetation sampling outlined a large gold anomaly 50 m downslope from the orebody and several other anomalies probably reflecting placer gold accumulations at the bedrock surface. Resistivity, induced polarization, ground magnetics and gravity were used to delineate drill targets. Subsequently, 3536m of core and reverse circulation drilling over a two year span outlined a zone of low-grade (0.04 opt gold) mineralized volcanic rock. Hole 34, a step-out drilled through alluvial cover west of the pediment, intersected 102m of silicified breccia that averaged 28 g/t gold and 62 g/t silver, and one vein containing visible, very high-grade gold. Drilling activity was accelerated and within 6 months a "probable" mining reserve of 1.45 million tons grading 0.32 opt Au and 0.90 opt Ag was defined. Overburden stripping started June, 1985, mining in January, 1986, and milling began in February, 1986. The original Sleeper Mine was developed and brought to production by Amax Gold and was mined through 1996.AMAX was later taken over by Kinross Gold, and in 2004, X-Cal bought out Kinross' remaining interest in the property and established a 50/50 joint venture with New Sleeper Gold Corporation to reevaluate and develop the mine property, deeper targets, and adjacent areas. IN 2002, X-Cal reported that eighty holes 35 feet deep had been completed by Sonic Drilling into 6.6 million tons of Sleeper tailings. The objective of the work was to better quantify some of the above-ground gold at the site as a possible offset to bonding and reclamation costs. in 2004, X-Cal reported an extensive program of geophysics, geochemistry, satellite imagery, and soil sampling as well as 3-D modeling and a thorough review of all data from Amax Gold. Past and recent drilling programs seem to verify the potential of multiple Sleeper-like and other major Nevada-type deposits. The company has identified above-ground resources of value and has also measured, indicated and inferred resources in the immediate vicinity of the existing Sleeper Pit. X-Cal has identified six favorable project domains within the 20,000 acre Sleeper Project: Sleeper Mine and vicinity (SM), Sleeper Ring - Rose Domal Uplift (SR),West Pediment (WP), Breccia Hill and South Pediment (BH), ZZ Top igneous center (ZZ) and Southeast igneous center (SE). The Sleeper deposit produced 1,685,500 ounces of gold and 2,334,400 ounces of silver from high-grade veins and lower grade stockwork and breccia ores. Ninety percent of the these ore mined was hosted by the Sleeper Rhyolite, a volcanic unit that is covered by alluvial gravels . The New Sleeper Gold joint venture controls approximately 27 square miles centered on the old Sleeper open pit. New Sleeper is aggressively exploring their ground for additional reserves and our claims are located on trend just 1.5 miles to the south

Reference information

Links to other databases

Agency Database name Acronym Record ID Notes
USGS Mineral Resources Data System MRDS M242534 MRDS dep_id 10047259 merged into this record.
USGS Mineral Resources Data System MRDS M242951 MRDS dep_id 10047579 merged into this record.
USGS Mineral Resources Data System MRDS W700408 MRDS dep_id 10084980 merged into this record.
U.S. Bureau of Mines Minerals Availability System MAS 320130499 MRDS dep_id 10173522 merged into this record.

Bibliographic references

  • Deposit

    Quade, Jack, 1985 - Attempted field examination report (locked gate, guard).

  • Deposit

    Nash, J.T., Utterback, W.C., and Saunders, J.A., 1991, Geology and Geochemistry of the Sleeper Gold Deposits, Humboldt County, Nevada, an interim report, in Raines, G.L., et al., eds., Geology and Ore Deposits of the Great Basin, The Geological Society of Nevada, Reno, p. 1063-1084.

  • Deposit

    Amax Annual Corporate Report for 1990, p. 18-19.

  • Deposit

    Wood, J.D., 1988, Geology of the Sleeper Gold Deposit, Humboldt County, Nevada, in Schafer, R., et al., eds., Bulk Mineable Precious Metal Deposits of the Western United States, The Geological Society of Nevada, Reno, p. 293-302.

  • Deposit

    Wood, J.D., 1987, Technical Aspects of the Sleeper Gold Discovery, Nevada, in Mining Technology and Policy Issues: 1986 International Mining Show, Las Vegas, Nevada, American Mining Congress, Washington, D.C., 3 pp.

  • Deposit

    Mining Magazine, January, 1989, p. 44.

  • Deposit

    Staff, 1988, Directory of Nevada Mine Operations Active During Calendar Year 1987: Nevada Division Of Mine Inspection, 84 p

  • Deposit

    Metal Market Consultants, Inc., 1987, Gold Situation Map.

  • Deposit

    Minesearch Annual, 1984-1985, Vol. VII, p. 418-420; Metals Economics Group, Boulder, Co.

  • Deposit

    Bonham, H.F., 1986, NBMG Field Examination Report, 5/86, and sample analyses.

  • Deposit

    Bonham, H.F., 1986, NBMG Map 91.

  • Deposit

    Bonham, H.F., 1988, in NBMG MI-1987.

  • Deposit

    NBMG Mining District File 123, Numerous Press Clippings and news releases

  • Deposit

    NBMG, 1994, MI-1993-2002

  • Deposit

    Nevada Division of Minerals, 1994

  • Deposit

    Mining Record, March 24, 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.

  • Deposit

    Saunders, James, 1994, Silica and gold textures in Bonanza Ores of the Sleeper Deposit, Humboldt County, Nevada: Econ. Geol. vol 89, pp. 628-638.

  • Deposit

    http://www.x-cal.com/sleeper.htm

  • Deposit

    Crafford, A.E.J. (ed.), 2003, GSN Road Log 2, Interstate 80 Eastbound, Fernley (Exit 48) to Golconda (Exit 194).

  • Reserve-Resource

    AMAX GOLD INC., 1995 ANNUAL REPORT; & FORM 10-K REPROT.

  • Deposit

    AMAX GOLD INC FORM 10K, 3/29/90

  • Deposit

    AMAX GOLD INC FORM 10K, 3/30/89

  • Deposit

    AMAX GOLD INC PROSPECTUS, 7/87

  • Deposit

    DEMULL, THOMAS J. ORE PROCESSING AT AMAX GOLD'S SLEEPER MINE, 12/87.

  • Deposit

    NEV. DIV. MINE INSPECTION, 1991, DIRECTORY OF NEVADA MINE OPERATIONS ACTIVE DURING CALENDAR YEAR 1990, P. 45.

  • Deposit

    HAMILTON, S. K. AND J. D. WOOD. THE SLEEPER GOLD-SILVER DEPOSIT DISCOVERY THROUGH FEASIBILITY, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES. NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.

  • Deposit

    POOLER, A. F. ENGINEERING AND OPERATIONS AT AMAX GOLD'S SLEEPER MINE, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES. NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.

  • Deposit

    STANFORD, W. D., AND T. J. DEMULL. AMAX GOLD'S SLEEPER MINE DEVELOPMENT AND CONSTRUCTION, IN ASSAYS TO ASSETS

  • Deposit

    UTTERBACK, W. C. GEOLOGY OF THE SLEEPER GOLD DEPOSIT, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES.

  • Deposit

    NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.

  • Deposit

    AMERICAN MINES HANDBOOK, 1996, PP. 19, 20, 21.

  • Deposit

    RANDOL MINING DIRECTORY, 1994/95, U.S. MINES & MINING COMPANIES, P351.

  • Deposit

    RANDOL MINING DIRECTORY, 1996/97, U.S. MINES & MINING COMPANIES, P272.

  • Deposit

    1995/96, NEVADA MINES DIRECTORY, PP. 2, 25.

  • Deposit

    THE NORTHERN MINER, VOL., #9, APRIL 28, 1997, P10.

  • Deposit

    AMAX GOLD INC., 1996 FORM 10-K, P8, AND ANNUAL REPORT.

General comments

Subject category Comment text
Deposit Ore was mined from high-grade veins and lower grade stockwork and breccia ores. The Sleeper deposit formed at about 15-16 Ma in a volcanic field during Basin-and-Range extension. Bonanza veins of uncommonly high gold grade are the most important ore type, but widespread zones of quartz stockwork and zones of breccia contain a sizable portion of bulk-mineable material. Both types of ore exhibit strong structural control in a brittle, formerly glassy rhyolite. The deposit is a combination of three superimposed ore types: 1) very high-grade bonanza veins, 2) medium grade breccias, and 3) lower grade stockworks. Multiple high-grade, banded quartz+adularia+Au veins are semi-continuous for more than 1200 m along strike and more than 500m down dip and comprise > 60% of reserves. The veins range up to 3m wide and generally dip 60-70W. Commonly, there is a zone comprised of many parallel and splaying veins spanning >30m with intervening breccias. Breccias cemented by silica, pyrite, and minor adularia typically contain 0.1 to 1 opt au with Au:Ag ratios ranging 3:1 to 6:1. Breccia ore generally is within 5m of high-grade veins but also occurs as discrete zones several meters wide in both footwall and hangingwall rocks. Approximately half of the breccia ore, chiefly that near veins, is processed through the mill. Stockwork ore containing numerous 1 to 10 mm wide quartz+pyrite veinlets generally grades <0.1 opt Au with Ag:Au ratios of 10:1. Stockwork ore is bulk mined for heap leaching. A small placer deposit has developed downslope from the ore deposit. Banded gold-silver veins at Sleeper exhibit similar textural features as veins at the National district. The gold content of the veins averages >20 opt and ranges to >170 opt. The veins contain more gold than silver. Hydrothermal breccias and stockwork veinlets formed after the high-grade veins and contain more silver than gold.
Deposit MINING WILL PROBOBLY STOP SOME TIME IN 1996 AS ORE IS DEPLETE LEACH PAD AND MILLING WILL PROCEED TILL ALL ORE IS PROCESSED. "LOWEST COST GOLD PRODUCER IN U.S." RANDOL 93-94
Environment Magmatism associated with continental extension under reducing conditions.
Environmental Factors PYRITE AND ARSENOPYRITE ASSOCIATED WITH HEAP, TAILS AND WASTE. TAILINGS ARE DILUTED BELOW TOXIC LEVELS.
Environmental Factors HEAP PAD HAS 60 MIL SYNTHETIC LINER AND 4 IN. RECOMPACTED CLAY UNDER SYNTHETIC LINER OVER ALLUVIUM. TAILINGS POND HAS MIN. 50 FT CLAY UNDER 12 IN. RECOMPACTED CLAY WITH PERMEABILITY COEFFICIENT NO GREATER THAN 10E-6 CM/SEC.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-SEP-85 La Pointe, D.D. (Tingley, J.V.) Nevada Bureau of Mines and Geology
Updater 01-AUG-88 Paidakovich, Matthew E. U.S. Geological Survey CHECKED AND MODIFIED ROCK TYPE, ROCK UNIT AND AGES FIELDS.
Updater 01-SEP-88 Schruben, Paul G. U.S. Geological Survey
Reporter 01-NOV-88 La Pointe, D.D. (Tingley, J.V.) Nevada Bureau of Mines and Geology
Updater 01-AUG-89 Beougher, Dee (Spanski, Gregory T.) U.S. Geological Survey
Updater 01-APR-92 Phinisey, J. D. (Marcus, S.) U.S. Geological Survey
Editor 01-SEP-94 Li, Zhiping (Moyer, Lorre A.) U.S. Geological Survey
Reporter 04-NOV-97 Buckingham, David A. U.S. Bureau of Mines
Reporter 01-MAY-04 LaPointe, D.D. Nevada Bureau of Mines and Geology
Editor 01-SEP-07 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.