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United States
Wharf Mine

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 Location:
16 km S from Spearfish, South Dakota, United States

  Address:
10928 Wharf Road
Lead
South Dakota, United States
57754
Phone  ...  Subscription required
Fax605-584-4188
WebsiteWeb
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  • Filings & News

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Overview

StageProduction
Mine TypeOpen Pit
Commodities
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Processing
  • Heap leach
  • Carbon in column (CIC)
  • Elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life7 years (as of Jan 1, 2020)


Owners & OPERATOR

Source: p. 14
CompanyInterestOwnership
Coeur Mining, Inc. 100 % Indirect
Wharf Resources U.S.A. Inc. (operator) 100 % Direct
Coeur owns 100% of Wharf Resources (U.S.A.) Inc., which operates the Wharf mine, an open-pit gold mine located near Lead, South Dakota.

Deposit Type

  • Epithermal
  • Sediment-hosted


Summary:

The Wharf Operation deposits are considered Tertiary epithermal replacement mineralization, both intrusive-hosted and sediment-hosted (Coeur internal report, 2014). Depth of mineralization at the Wharf Operation (~1.5 km; Paterson and Giebink, 1989) is considered deeper than normal for epithermal deposits, but low temperature of mineralization are consistent with epithermal-type deposits (Paterson, 1990), although these temperatures may represent late stage of fluorite mineralization.

The main trends of mineralization at Wharf parallel the strike of a major joint sets that Shapiro and Gries (1970) measured in upper and lower Deadwood Fm. outcrops. At Golden Reward, the mineralized trends strike north-south. Mineralized trends at Golden Reward may reflect more of an influence from basement structure, as the later faults in the Golden Reward graben area may have been reactivated along faults or moved along existing foliation planes, and mineralization occurred along the same trend as the faulting.

Gold or gold-bearing minerals may be disseminated in porphyry, or may be confined to fractures (Paterson and Giebink, 1989; Paterson, 1990). Highly fractured porphyry is known to be the most mineralized, and preliminary work shows a correlation of fractured porphyry with gold, in contrast to unfractured and unmineralized rocks within mineralized zones. This, however, may be due again to gold-bearing sulfides occurring as the primary economic mineral. Porphyry near fractures is usually the most oxidized, grading outwards into gray, blocky porphyry with very small (< 0.25 mm) grains of disseminated sulfides. Atomic absorption (AA) assaying is limited in determining gold encapsulated in sulfides, but assays of fractured samples that are oxidized will readily measure gold formerly in sulfides. Additional fire assays may help to better understand this association.

Visible native gold observed at Wharf has been only seen twice during current mining activities; one occurrence was found within a fluorite vein. Because fluorite is considered a late-stage mineral (e.g., Paterson et al., 1989), the fluorite-gold occurrence may indicate a later, minor mineralizing event, distinct from earlier, goldbearing sulfide mineralization. Thin sections of very high-grade (1.173 and 0.615 oz/ton Au) samples from the Annie Creek mine analyzed by Schurer and Fuchs (1991) show native gold associated with hematite, goethite, jarosite which forms from oxidation of iron sulfides, and arseniosiderite which forms from oxidation of arsenopyrite; quartz was also associated with gold. A thin section from the lowestgrade sample in this study (0.195 oz/ton Au) showed no native gold, but abundant sulfides, which was assumed to indicate lattice or submicron gold. The discussion suggests that oxidation of arsenic-bearing sulfides may have remobilized gold in an arsenic complex and deposited it as native gold in higher-grade samples (Schurer and Fuchs, 1991).


Mining Methods

  • Truck & Shovel / Loader


Summary:

The Wharf Operation is currently a conventional truck and loader heap leach gold mine. The Wharf Operation consists of five heap leach pads, which are all load/offload pads. The entire planned mining disturbance falls within the current permitted area.

Wharf leases nearly all of the earth moving equipment used at the mine. The current earth moving equipment under lease through local equipment dealers includes: (14) 777 trucks, (1) D-10 and (2) D-9 dozers, (4) 993 front end loaders, (2) 16M motor graders, and (2) DM 45 hammer drills. Relationships with local dealers span over 15 years, and the earthmoving equipment is under contract through 2017.


Crushing and Grinding


Processing

  • Heap leach
  • Carbon in column (CIC)
  • Elution
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

Ore is trucked to the crusher located at the east end of the plant/pad area to be crushed to a nominal size of 80 percent minus ¾-inch passing. The crushing plant can process between 4.2 and 4.6M tons of ore per year, depending on ore hardness. Lime is added to the crushed ore. Once crushed, the ore is trucked to leach pads to be stacked in 20-foot-high lifts.

Stacked ore is then leached with dilute sodium cyanide solution. Gold and silver in the pregnant (metal-bearing) leach solution (PLS) are recovered by adsorption on activated carbon and the barren (non-metal bearing) leach solution is recycled to the heap leach pad. Spent ore is rinsed, neutralized and denitrified and then removed from the leach pad to be placed on a designated spent ore storage area.

Gold and silver is recovered from loaded carbon utilizing a modified pressure Zadra method. The rich electrolyte (RE) from the elution process is then processed by electrowinning, depositing the metals int ........

Recoveries & Grades:

CommodityParameter20192018201720162015
Gold Head Grade, oz/ton 0.020.020.030.030.03
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Production:

CommodityUnits202020192018201720162015
Gold oz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required95,372109,17578,132
Silver oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Equivalent oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics201920182017201620152014
Tonnes milled  ......  Subscription required  ......  Subscription required  ......  Subscription required4,268,105 tons3,600,279 tons4,201,362 tons
Ore tonnes mined  ......  Subscription required  ......  Subscription required  ......  Subscription required4,190,362 tons
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven 23,436,000 tons Gold 0.024 oz/ton 571,000 oz
Probable 7,530,000 tons Gold 0.026 oz/ton 197,000 oz
Proven & Probable 30,965,000 tons Gold 0.025 oz/ton 768,000 oz
Measured 6,631,000 tons Gold 0.027 oz/ton 178,000 oz
Indicated 4,926,000 tons Gold 0.032 oz/ton 156,000 oz
Measured & Indicated 11,557,000 tons Gold 0.029 oz/ton 334,000 oz
Inferred 2,483,000 tons Gold 0.033 oz/ton 81,000 oz

Commodity Production Costs:

CommodityUnits202020192018201720162015
Total cash costs (sold) Gold Equivalent USD  ......  Subscription required 697 / oz 606 / oz 706 / oz
Total cash costs (sold) Gold USD  ......  Subscription required ^†  ......  Subscription required†  ......  Subscription required† 693 / oz†
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Financials:

Units202020192018201720162015
Capital expenditures (planned) M USD  ......  Subscription required
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 3.21  
Sustaining costs M USD  ......  Subscription required  ......  Subscription required 3.2  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 84.1  
After-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 12.9  
Operating Cash Flow M USD  ......  Subscription required  ......  Subscription required 32  
Subscription required - Subscription is required


Heavy Mobile Equipment as of February 7, 2018:
HME TypeModelQuantityLeased or
Contractor
Dozer ....................... Subscription required 1
Dozer ....................... Subscription required 4
Dozer ....................... Subscription required 1 Leased
Drill ....................... Subscription required 2
Drill ....................... Subscription required 1
Drill ....................... Subscription required 2 Leased
Grader ....................... Subscription required 2 Leased
Loader (FEL) ....................... Subscription required 4 Leased
Truck (haul) ....................... Subscription required 4 Leased
Truck (haul) ....................... Subscription required 10 Leased
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Sep 17, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 17, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 17, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 17, 2020
Subscription required - Subscription is required.

Staff:

EmployeesYear
Subscription required 2019
Subscription required 2018
Subscription required 2017
Subscription required 2016
Subscription required 2015

Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
................................... Subscription required 2018
Annual Report 2017
Year-end Mineral Reserves 2017
Annual Report 2016
Press Release 2016
Press Release 2016
Year-end Mineral Reserves 2016
Annual Report 2015
Technical Report 2015
Year-end Mineral Reserves 2015
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Aerial view:

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