Sleeper Mine

Site Name

Primary: Sleeper Mine
Secondary: Sleeper Pit
Secondary: Wood Pit
Secondary: West Wood
Secondary: Bedrock Casino
Secondary: Northeast areas

---

Commodity

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

---

Location

State: Nevada
County: Humboldt
District: Amos District

---

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: Winnemucca BLM District

---

Holdings

Not available

---

Workings

Type: Surface

---

Ownership

Owner Name: Nevada Gold Mining, Inc. (100% sub of Amax Gold Inc.)
Home Office: Nevada
Info Year: 1996
Years: 1991 - 1996

Owner Name: Amax Gold, Inc.
Company ID: 2670255
Percent: 100.0
Home Office: Colorado
Info Year: 1996
Years: 1990 - 1996

Owner Name: Amax Gold, Inc.
Percent: 50.00
Home Office: Colorado
Info Year: 1996
Years: 1996 - 1997

Owner Name: X-Cal Resources
Percent: 50.00
Home Office: Canada
Info Year: 1996
Years: 1996 - 1997

Owner Name: X-Cal Resources
Percent: 100.0
Home Office: Canada
Info Year: 1997
Years: 1997 -

Owner Name: Owner listed as Amax, Inc.
Years: 1987 -

Owner Name: Nevada Gold Mining, Inc.
Years: 1988 -

Owner Name: Amax Inc. (Nevada Gold Mining Inc., a wholly-owned subsidiary of Amax)
Years: 1988 -

Owner Name: Amax Gold, Inc.

Owner Name: Sleeper Joint Venture partners, X-Cal Resources Ltd.
Percent: 50.00
Info Year: 2004

Owner Name: Sleeper Joint Venture partners, New Sleeper Gold Corporation (TSX-V: NWS)
Percent: 50.00
Info Year: 2004

---

Production

Year: 1995
Description: Gold Production (Hl Gold-27,331 Tr Oz) 82062 Tr Oz
Year: 1996
Description: Ore Milled @ 0.069 Tr Oz/St 570975 St Ore
Year: 1996
Description: Ore Heap Leached @ 0.02 Tr Oz/St 454100 St Ore
Year: 1996
Description: Gold Production (Hl Gold-12,356 Tr Oz) 38199 Tr Oz
Year: 1986
Description: 168265 Mt Milled 4124000 Grams Au
Year: 1987
Description: 267067 Mt Milled, 910,194 Mt Leached 4936000 Grams Au
Year: 1988
Description: 344449 Mt Milled, 4,401,190 Mt Leached 7167000 Grams Au
Year: 1989
Description: 492735 Mt Milled, 4,777,315 Mt Leached 7969000 Grams Au
Year: 1991
Description: Silver Production 9003308 Grams
Year: 1994
Description: Ore Milled @ 0.11 Tr Oz/St 802534 St Ore
Year: 1994
Description: Ore Heap Leadhed @ 0.016 Tr Oz/St 5012600 St Ore
Year: 1994
Description: Gold Production (Hl Gold-36,162 Tr Oz) 106912 Tr Oz
Year: 1995
Description: Ore Milled @ 0.095 Tr Oz/St 857284 St Ore
Year: 1995
Description: Ore Heap Leached @ 0.018 Tr Oz/St 2779000 St Ore

---

Deposit

Record Type: Site
Operation Category: Producer
Deposit Type: hydrothermal -vein, -stockwork/stringers, -breccia filling
Operation Type: Surface
Milling Method: Heap Leach-Agglomerate-Carbon Column-Electrowin
Year First Production: 1986
Year Last Production: 1996
Discovery Year: 1982
Discovery Method: Geochemical And Geophysical Anomaly
Years of Production:
Organization:
Significant: Y
Deposit Size: M

---

Physiography

Not available

---

Mineral Deposit Model

Model Name: Epithermal vein, Comstock

---

Orebody

Form: tabular to disseminated to irregular

Not available

---

Structure

Type: R
Description: In the northern Slumbering Hills, Triassic sedimentary rocks are weakly folded and form a N20E-trending monocline that dips 45 east.

Type: L
Description: 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.

---

Alterations

Alteration Type: L
Alteration Text: 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.

---

Rocks

Name: Quartzite
Role: Host
Age Type: Host Rock
Age Young: Early Jurassic
Age Old: Late Triassic

Name: Slate
Role: Host
Age Type: Host Rock
Age Young: Early Jurassic
Age Old: Late Triassic

Name: Phyllite
Role: Host
Age Type: Host Rock
Age Young: Early Jurassic
Age Old: Late Triassic

Name: Andesite
Role: Host
Age Type: Host Rock
Age Young: Miocene

Name: Porphyry
Role: Host
Description: Rhyolite
Age Type: Host Rock
Age Young: Miocene

Name: Rhyolite
Role: Host
Description: porphyry
Age Type: Host Rock
Age Young: Miocene

---

Analytical Data

Analytical Data: 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.
Analytical Data: Al commonly is mobile. Ore zones are enriched in As and Se and are sporadically enriched in Sb, Hg, Tl, and Mo
Analytical Data: All rocks in the pit are enriched in K and S, and depleted in Ca and Na

---

Materials

Ore: Gold
Gangue: Illite
Gangue: Barite
Gangue: Kaolinite
Gangue: Alunite
Gangue: Sericite
Gangue: Cristobalite
Gangue: Opal
Gangue: Marcasite
Gangue: Pyrite
Gangue: Stibnite
Gangue: Adularia
Gangue: Quartz
Gangue: Jarosite

---

Comments

Comment (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.

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

Comment (Geology): 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).

Comment (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.

Comment (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.

Comment (Workings): 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.

Comment (Location): The mine is located in Desert Valley on the NW Flank of the Slumbering Hills.

Comment (Commodity): Ore Materials: native gold

Comment (Commodity): Gangue Materials: quartz, adularia, stibnite, pyrite, marcasite, opal, cristobalite, sericite, alunite, kaolinite, smectite, barite, illite, jarosite.

Comment (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

Comment (Environmental Factors): PYRITE AND ARSENOPYRITE ASSOCIATED WITH HEAP, TAILS AND WASTE. TAILINGS ARE DILUTED BELOW TOXIC LEVELS.

Comment (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

Comment (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.

---

References

Reference (Deposit): DEMULL, THOMAS J. ORE PROCESSING AT AMAX GOLD'S SLEEPER MINE, 12/87.

Reference (Reserve-Resource): AMAX GOLD INC., 1995 ANNUAL REPORT; & FORM 10-K REPROT.

Reference (Deposit): AMAX GOLD INC FORM 10K, 3/30/89

Reference (Deposit): RANDOL MINING DIRECTORY, 1994/95, U.S. MINES & MINING COMPANIES, P351.

Reference (Deposit): RANDOL MINING DIRECTORY, 1996/97, U.S. MINES & MINING COMPANIES, P272.

Reference (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.

Reference (Deposit): NEV. DIV. MINE INSPECTION, 1991, DIRECTORY OF NEVADA MINE OPERATIONS ACTIVE DURING CALENDAR YEAR 1990, P. 45.

Reference (Deposit): AMAX GOLD INC FORM 10K, 3/29/90

Reference (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.

Reference (Deposit): 1995/96, NEVADA MINES DIRECTORY, PP. 2, 25.

Reference (Deposit): AMERICAN MINES HANDBOOK, 1996, PP. 19, 20, 21.

Reference (Deposit): NORTHWEST MIN. ASSOC., SPOKANE, WA, DEC. 1987.

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

Reference (Deposit): AMAX GOLD INC PROSPECTUS, 7/87

Reference (Deposit): AMAX GOLD INC., 1996 FORM 10-K, P8, AND ANNUAL REPORT.

Reference (Deposit): THE NORTHERN MINER, VOL., #9, APRIL 28, 1997, P10.

Reference (Deposit): UTTERBACK, W. C. GEOLOGY OF THE SLEEPER GOLD DEPOSIT, IN ASSAYS TO ASSETS RECENT FEASIBILITY CASE HISTORIES.

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

Reference (Deposit): http://www.x-cal.com/sleeper.htm
URL: http://www.x-cal.com/sleeper.htm

Reference (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.

Reference (Deposit): Minesearch Annual, 1984-1985, Vol. VII, p. 418-420; Metals Economics Group, Boulder, Co.

Reference (Deposit): Metal Market Consultants, Inc., 1987, Gold Situation Map.

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

Reference (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.

Reference (Deposit): Mining Magazine, January, 1989, p. 44.

Reference (Deposit): Amax Annual Corporate Report for 1990, p. 18-19.

Reference (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.

Reference (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.

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

Reference (Deposit): Mining Record, March 24, 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.

Reference (Deposit): NBMG, 1994, MI-1993-2002

Reference (Deposit): Nevada Division of Minerals, 1994

Reference (Deposit): NBMG Mining District File 123, Numerous Press Clippings and news releases

Reference (Deposit): Bonham, H.F., 1988, in NBMG MI-1987.

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

Reference (Deposit): Bonham, H.F., 1986, NBMG Field Examination Report, 5/86, and sample analyses.

---

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.