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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
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • 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 Life8 years (as of Jan 1, 2021)


Owners

Source: p. 22
CompanyInterestOwnership
Wharf Resources U.S.A. Inc. (operator) Direct
Coeur Mining, Inc. 100 % Indirect
The Wharf mine operated by wholly-owned subsidiaries, Wharf Resources (U.S.A.) Inc. and Golden Reward Mining Limited Partnership.

Deposit Type

  • Epithermal
  • Sediment-hosted
  • Vein / narrow vein


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:

Wharf Operation is currently a conventional truck and loader heap leach gold mine. The mine has been in continuous operation since 1983. Wharf leases nearly all the earth moving equipment used at the mine.

In-situ ore and waste must be blasted prior to removal. Several historic pits that were partially backfilled are being mined again and the backfilled material is considered rehandle and does not require blasting. Waste material removed for access to the ore is taken to one of the rock disposal sites. Rock disposal sites are all designed to fill existing pits and are reclaimed as soon as possible after placement.


Crushing and Grinding
Flow Sheet: Source
Crusher / Mill TypeModelSizePowerQuantity
Jaw crusher ....................... Subscription required 1
Cone crusher ....................... Subscription required 1
Cone crusher ....................... Subscription required 4

Summary:

Crushing
A single crushing circuit is used to process ore before being transferred to the leach pads. This crushing circuit has undergone numerous modifications over its history to accommodate operational conditions and optimize performance.

Ore is hauled from the pit with CAT 777 and 785 haul trucks that dump directly into a hopper or onto a stockpile adjacent to the hopper. Stockpiled ore is fed into the hopper by a loader at times when a direct ore haul is not available.

Ore is transferred by an apron chain feeder to a vibrating grizzly where oversize rock is diverted in to a Nordberg C140 jaw crusher. The jaw crusher reduces the rock down to a 6-inch nominal size before dropping onto a conveyor belt along with the fines from the grizzly. Powdered lime is added to the ore from a silo as it is conveyed up to the secondary crushing stage. The lime application rate can be adjusted as needed to control solution pH during leaching.

Before being fed into the secondary crusher, the ore passes over a screen deck to remove final product sized material. These fines are conveyed to the final product pile and oversize rock drops into a Nordberg HP 500 cone crusher where it is reduced to 2 ½ inch nominal size. Crushed ore is then conveyed to an adjacent screen plant to remove product size material before being conveyed to the tertiary crushing stage.

The tertiary stage of the crushing system consists of four Nordberg Omnicone 1560 cone crushers. Ore enters the tertiary stage through a diverter that distributes the rock to the four cone crushers. Each cone has its own screen deck to remove product size material before dropping into the crusher. This product size material is conveyed to the final product pile. Rock that is larger than product size falls in the tertiary cones and is crushed down to ¾-inch nominal size. The total crushing system throughput of 750 to 1,000 tons per hour can be achieved with only three of the tertiary cones operating. A fourth cone can be left in standby in the event of a failure or planned maintenance on one of the other cones.

After leaving the tertiary crushers the ore is conveyed back to the screen plant and any material not meeting the final product size is recirculated back into the tertiary cones until it meets specifications. The final product size target is 90 percent passing ¾-inch and 80 percent passing ½-inch.


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 into an ........

Recoveries & Grades:

CommodityParameter2021202020192018201720162015
Gold Head Grade, oz/ton  ......  Subscription required  ......  Subscription required  ......  Subscription required0.020.030.030.03
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required94.389.5

Production:

CommodityUnits2022202120202019201820172016
Gold oz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required76,84095,372109,175
Silver oz  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Equivalent oz  ......  Subscription required  ......  Subscription required  ......  Subscription required
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics202120202019201820172016
Ore tonnes mined  ......  Subscription required  ......  Subscription required4,829,735 tons
Tonnes milled  ......  Subscription required  ......  Subscription required4,613,359 tons4,923,774 tons4,560,441 tons4,268,105 tons
Stripping / waste ratio  ......  Subscription required  ......  Subscription required1.85
Subscription required - Subscription is required.

Reserves at December 31, 2021:
Mineral Reserve and Mineral Resource reported above a gold cut-off grade of 0.010 oz/ton Au.

CategoryTonnage CommodityGradeContained Metal
Proven 27,976 k tons Gold 0.022 oz/ton 621 koz
Probable 8,306 k tons Gold 0.028 oz/ton 231 koz
Proven & Probable 36,282 k tons Gold 0.023 oz/ton 852 koz
Measured 13,947 k tons Gold 0.02 oz/ton 273 koz
Indicated 6,379 k tons Gold 0.022 oz/ton 139 koz
Measured & Indicated 20,326 k tons Gold 0.02 oz/ton 412 koz
Inferred 3,724 k tons Gold 0.024 oz/ton 90 koz

Commodity Production Costs:

CommodityUnits2021202020192018201720162015
Total cash costs (sold) Gold Equivalent USD 880 / oz 697 / oz 606 / oz 706 / oz
Total cash costs (sold) Gold USD  ......  Subscription required†  ......  Subscription required†  ......  Subscription required† 879 / oz† 693 / oz†
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units20212020
OP mining costs ($/ton mined) USD 3.054.25
Processing costs ($/ton milled) USD  ......  Subscription required  ......  Subscription required
G&A ($/ton milled) USD  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Financials:

Units2022202120202019201820172016
Capital expenditures (planned) M USD  ......  Subscription required
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required3.4   8.8   4.8  
Sustaining costs M USD 5.8   4.8  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required96.5   125.9   136.7  
After-tax Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required13.5   36.9   43.1  
Operating Cash Flow M USD 49.6   62.4  
Subscription required - Subscription is required


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

Mine Management:

Job TitleNameEmailProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Feb 25, 2022
....................... Subscription required ....................... Subscription required Subscription required Feb 25, 2022
....................... Subscription required ....................... Subscription required ....................... Subscription required Subscription required Feb 25, 2022
....................... Subscription required ....................... Subscription required Subscription required Feb 25, 2022
Subscription required - Subscription is required.

Staff:

EmployeesYear
Subscription required 2021
Subscription required 2020
Subscription required 2019
Subscription required 2018
Subscription required 2017
Subscription required 2016
Subscription required 2015

Corporate Filings & Presentations:

DocumentYear
Corporate Presentation 2022
................................... Subscription required 2021
................................... Subscription required 2021
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
Form 10-K 2018
Press Release 2018
Technical Report 2018
Year-end Mineral Reserves 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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