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United States
Greens Creek Mine

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 Location:
27 km SW from Juneau, Alaska, United States

  Address:
Admiralty Island
Juneau
Alaska, United States
99803
Phone  ...  Subscription required
WebsiteWeb
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Silver
  • Gold
  • Lead
  • Zinc
Mining Method
  • Cut & Fill
  • Longhole stoping
  • Paste backfill
Processing
  • Gravity separation
  • Flotation
Mine Life11 years (as of Jan 1, 2019)
Latest NewsHecla Reports Record Silver, Gold and Lead Reserves     February 14, 2019


Owners

 
CompanyInterestOwnership
Hecla Mining Company 100 % Indirect
Hecla Greens Creek Mining Company 100 % Direct

Deposit Type

  • Hybrid


Summary:

Work by Taylor and Johnson (2010) in the USGS Professional Paper 1763 indicated that the Greens Creek deposit displays a range of syngenetic, diagenetic, and epigenetic features that are typical of volcanic massive sulfide deposits (VMS), sedimentary exhalative (SEDEX), and Mississippi Valley-type (MVT) genetic models. Based on those observations the investigators indicated that the Greens Creek mineral deposit was a ‘hybrid’ type with elements of several deposit models.

Due to variations in mineralization, structural complexity, and spatial location, the Greens Creek mineralization is segregated into nine separate mineralized zones. In order from easternmost and highest elevations to westernmost, the zones are:

• East
• West
• 9A
• Northwest West
• Upper Plate
• 5250
• Southwest
• 200 South
• Gallagher.

On a gross deposit scale the mineralization trends N 30° W and plunges to the south at approximately 20°. The East Zone outcrops at the eastern edge of the mineral deposit, dips to the west, and transitions into the West Zone near a tight F2 fold where the mineral horizon transitions from a nearly flat orientation to a nearly vertical wall dipping steeply to the west. The East and West zones are bounded on the west by the Maki Fault system which offset the mineral horizon to the north in a dextral sense. The western deformation boundary of the Maki Fault tends to be a continuous fault splay which is called the Kahuna Fault. The mineralization hosted inside the fault zone are called the 9A Zone.

West of the Kahuna Fault, the Northwest West Zone represents the offset portion of the West Zone. Above and to the south of the Northwest West Zone is the main trend of mineralization which includes the Southwest Zone followed by the 200S Zone further down plunge. The 5250 Zone is the along the upper mineralized trend evidenced in the East Zone, just offset across the Maki-Kahuna Fault system.

The Gallagher Zone lies to the west of the 200 South Zone and is west of a second major dextral fault zone known as the Gallagher Fault. Offset on a post-mineralized dike swarm, the trend of the 200S Zone into the Gallagher Fault and the similar structural and chemical styles between the southern 200S and Gallagher mineral zones all indicate that the Gallagher Zone is simply the fault offset of the 200S Zone.


Mining Methods

  • Cut & Fill
  • Longhole stoping
  • Paste backfill


Summary:

The mine is primarily accessed via the 920-level portal in the same general area as the mill, stockpile pad and administration building. This portal also serves as the primary air intake. A second portal adjacent to the 920 Portal serves as a secondary escapeway and an additional air intake. A third portal located at the 1350 elevation serves as the primary ventilation exhaust and an additional escapeway. There is also a raisebored ventilation raise to the 1350 portal area which serves as an additional exhaust.

The working areas are accessed via ramp. Most ramps are connected with crosscuts at various locations, therefore most working areas have multiple options for equipment access in the event a particular ramp is blocked for rehab or utility work. Two of the ramp systems have a single route for mobile equipment access. These ramps feature laddered escapeway raises to enable airflow and a secondary means of egress.

Mine production and development are undertaken with modern mechanized trackless equipment. Ore and waste are hauled to the surface using trucks. Backfill is achieved using a combination of three methods: paste pumped from the underground paste plant, cemented tailings trucked and jammed and into the heading, and development waste placed into the area to be backfilled. In addition to the conventional trackless mining equipment, the Greens Creek fleet contains one LHD capable of semi-autonomous operation and another LHD capable of teleremote operation. This equipment enables production activities to continue during the shift change and post-blasting periods when no personnel are allowed underground.

The current production rate is 2,300 t/d of which approximately 2,000 t/d is produced by cut-and- fill with the remaining 300 t/d from longhole stoping. Longhole Mineral Reserves are projected to be depleted approximately halfway through the remaining mine life, at which point the mine plan calls for 2,300 t/d of production from cut-andfill mining.


Crushing and Grinding


Processing

  • Gravity separation
  • Flotation

Flow Sheet: Subscription required

Summary:

The Greens Creek mill produces three saleable flotation concentrates and a gravity concentrate. A carbon concentrate is produced as part of the process but is discarded as part of tailings.

A gravity circuit utilizing spiral concentrators treats a bleed stream from the grinding circuit cyclones. It produces a final gravity concentrate that is further processed offsite. Lead concentrate is produced in a rougher-cleaner circuit with re-grinding of the cleaner feed. The lead concentrate is relatively low grade, at approximately 35% lead, but carries a large proportion of the silver in mill feed.

Zinc concentrate is produced in a rougher-cleaner circuit, also with re-grinding, using lead rougher tailings as feed. The zinc concentrate typically contains 46 to 50% zinc, which is a normal grade, and considerably less silver than the lead concentrate.

Bulk concentrate is produced in a complex circuit which has as feed cleaner tailings from both the lead and ........

Recoveries & Grades:

CommodityParameter20192018201720162015201420132012
Silver Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Silver Head Grade, % 14.612.212.914.613.513.21311.1
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Head Grade, oz/ton 0.10.090.090.10.110.120.120.12
Lead Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Lead Head Grade, % 2.922.82.723.113.33.223.333.49
Zinc Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Zinc Head Grade, % 7.437.477.258.088.748.388.479.35
Subscription required - Subscription is required.

Production:

CommodityProductUnits202020192018201720162015
Silver Metal in conc./ doré koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required8,3529,2548,452
Gold Metal in conc./ doré koz  ......  Subscription required ^  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Lead Metal in concentrate tons  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Zinc Metal in concentrate tons  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
^ Guidance / Forecast.
Subscription required - Subscription is required.

Operational Metrics:

Metrics2019201820172016201520142011
Tonnes milled  ......  Subscription required  ......  Subscription required  ......  Subscription required815,639 tons814,398 tons816,213 tons772,069 tons
Daily milling rate  ......  Subscription required  ......  Subscription required  ......  Subscription required2,229 tons2,231 tons
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven 7 k tons Silver 14.8 oz/ton 106 koz
Proven 7 k tons Gold 0.08 oz/ton 1 koz
Proven 7 k tons Lead 2.6 % 180 tons
Proven 7 k tons Zinc 5.4 % 390 tons
Probable 10,713 k tons Silver 12.2 oz/ton 130,791 koz
Probable 10,713 k tons Gold 0.09 oz/ton 932 koz
Probable 10,713 k tons Lead 2.8 % 305,010 tons
Probable 10,713 k tons Zinc 7.3 % 778,020 tons
Proven & Probable 10,721 k tons Silver 12.2 oz/ton 130,897 koz
Proven & Probable 10,721 k tons Gold 0.09 oz/ton 932 koz
Proven & Probable 10,721 k tons Lead 2.8 % 305,190 tons
Proven & Probable 10,721 k tons Zinc 7.3 % 778,410 tons
Measured 76 k tons Silver 12.5 oz/ton 949 koz
Measured 76 k tons Gold 0.09 oz/ton 7 koz
Measured 76 k tons Lead 2.6 % 2,000 tons
Measured 76 k tons Zinc 9.4 % 7,140 tons
Indicated 8,569 k tons Silver 11.7 oz/ton 100,187 koz
Indicated 8,569 k tons Gold 0.1 oz/ton 828 koz
Indicated 8,569 k tons Lead 2.8 % 242,010 tons
Indicated 8,569 k tons Zinc 8.1 % 691,750 tons
Measured & Indicated 8,645 k tons Silver 11.7 oz/ton 101,135 koz
Measured & Indicated 8,645 k tons Gold 0.1 oz/ton 835 koz
Measured & Indicated 8,645 k tons Lead 4.9 % 244,010 tons
Measured & Indicated 8,645 k tons Zinc 8.1 % 698,880 tons
Inferred 1,848 k tons Silver 13.7 oz/ton 25,393 koz
Inferred 1,848 k tons Gold 0.09 oz/t 159 koz
Inferred 1,848 k tons Lead 3.1 % 56,670 tons
Inferred 1,848 k tons Zinc 7.4 % 135,880 tons

Commodity Production Costs:

CommodityUnits20202019201820172016
Credits (by-product) Silver USD  ......  Subscription required  ......  Subscription required -21.83 / oz -17.48 / oz
Cash costs Silver USD  ......  Subscription required  ......  Subscription required 22.5 / oz 21.3 / oz
Cash costs Silver USD  ......  Subscription required ^†  ......  Subscription required†  ......  Subscription required† 0.71 / oz† 3.84 / oz†
All-in sustaining costs (AISC) Silver USD  ......  Subscription required  ......  Subscription required 27.6 / oz 26.9 / oz
All-in sustaining costs (AISC) Silver USD  ......  Subscription required ^†  ......  Subscription required†  ......  Subscription required† 5.76 / oz† 9.42 / oz†
^ Guidance / Forecast.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units2019201820172016201520142013
UG mining costs ($/ton milled) USD 80.671.470.969.571.569.568.4
Processing costs ($/ton milled) USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Financials:

Units2019201820172016201520142013
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 46   31.5  
Operating Income M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 26.5   39.8   62.2  
Gross profit M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 32.6   45.5   69.7  
Subscription required - Subscription is required


Heavy Mobile Equipment as of December 31, 2018:
HME TypeModelQuantity
Dozer (crawler) ....................... Subscription required 2
Drill (long hole) ....................... Subscription required 1
Drill (long hole) ....................... Subscription required 1
Grader ....................... Subscription required 2
Jumbo ....................... Subscription required 1
Jumbo ....................... Subscription required 1
Jumbo ....................... Subscription required 2
Jumbo ....................... Subscription required 2
Load-Haul-Dump (LHD) ....................... Subscription required 4
Load-Haul-Dump (LHD) ....................... Subscription required 1
Load-Haul-Dump (LHD) ....................... Subscription required 7
Load-Haul-Dump (LHD) ....................... Subscription required 1
Rock bolter ....................... Subscription required 4
Rock bolter ....................... Subscription required 1
Rock bolter ....................... Subscription required 1
Rock bolter ....................... Subscription required 1
Rock bolter ....................... Subscription required 1
Rock bolter ....................... Subscription required 1
Trans Mixer ....................... Subscription required 1
Truck (haul) ....................... Subscription required 7
Truck (haul) ....................... Subscription required 1
Underground truck ....................... Subscription required 4
Underground truck ....................... Subscription required 5
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 2020
....................... Subscription required ....................... Subscription required Subscription required Sep 24, 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 2018
................................... Subscription required 2018
................................... Subscription required 2018
Form 10-K 2017
Form 10-K 2016
Annual Report 2015
Form 10-K 2015
Year-end Mineral Reserves 2015
Annual Report 2014
Subscription required - Subscription is required.

News:

NewsDate
Hecla Reports Record Silver, Gold and Lead Reserves February 14, 2019

Aerial view:

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