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United States
North Bullfrog - Mother Lode Project

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 Location:
12 km N from Beatty, Nevada, United States

  Project Contacts:
Suite 1750-700 West Pender Street
Vancouver
British Columbia, Canada
V6C 1G8
Phone  ...  Subscription required
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  • Filings & News

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Overview

StagePreliminary Economic Assessment
Mine TypeOpen Pit
Commodities
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Processing
  • Gravity separation
  • Flotation
  • ROM/dump leach
  • Counter current decantation (CCD)
  • Concentrate leach
  • Pressure oxidation
  • Carbon in leach (CIL)
  • Carbon in column (CIC)
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life9 years (as of Jan 1, 2018)
Latest NewsCorvus Gold Expands Mother Lode Deposit Intersects New Deep Intrusive Zone Below Main Deposit with 50.3m @ 1.50 g/t Gold     December 5, 2019


Owners

 
CompanyInterestOwnership
Corvus Gold Inc. 100 % Direct

Deposit Type

  • Epithermal
  • Carlin-type
  • Sediment-hosted
  • Volcanic hosted


Summary:

Mineralization at MLP most closely resembles Carlin-type sediment-hosted gold systems of northern Nevada. The Mother Lode deposit model includes structurally and stratigraphically- controlled disseminated sulfide and oxide mineralization hosted in primarily in Tertiary sedimentary rocks and rhyolite porphyry dikes. Paleozoic sedimentary rocks comprise a smaller volume host in proximity to dikes and the basal Tertiary unconformity. Tertiary volcanic rocks and debris flow breccias are also mineralized at Mother Lode. Alteration types associated with gold mineralization include passive decalcification and illite-pyrite alteration. Unique features of Mother Lode-style mineralization compared to typical Carlin-type deposits include: the association with fluorine, the significant volume of mineralization that is rhyolite porphyry dikehosted, elevated tellurium and bismuth, and the generally passive, innocuous, very low-silica nature of the mineralization. Carlin-type gold deposits are generally known to form at depths of >2 kilometres, at temperatures between 180-240o C. Mineralization at Mother lode may have formed at depths of 500-1000 metres or less, and at temperatures <240o C (Weiss, 1996).

Gold mineralization in the main Bullfrog and North Bullfrog sub-districts is characterized as volcanic-hosted low-sulfidation epithermal type. Two styles of epithermal precious metal mineralization are present: 1) disseminated mineralization associated with sulfidation of iron in the volcanic host rocks; and 2) open-space filling quartz and/or carbonate veins, which are controlled by boiling. Pervasive quartz-adularia alteration of volcanic rocks is intimately associated with the disseminated mineralization and is an important ground preparation process for later vein forming events. Epithermal deposits form at shallow depth, from the surface to generally <2 kilometres. Temperatures of formation range between 150 to 300°C. Mineralization at NBP is typical of other low-sulfidation type gold systems in and around the Walker Lane trend such as: Bullfrog, Round Mountain, Rawhide, Aurora, Bodie and Comstock. These deposits commonly contain higher grade gold in vein and stockwork zones surrounded by zones of lower grade disseminated mineralization. This is the accepted exploration model at NBP.


Mining Methods

  • Truck & Shovel / Loader


Summary:

Conventional surface mining methods using surface drill and blast techniques with off highway haul trucks and front-end loaders will be employed at both the Mother Lode open pit and the North Bullfrog open pits. Higher grade mineralization from the YellowJacket vein and vein stockwork, and any Sierra Blanca sulfide mineralization with sufficient grade would be trucked on Highway 95 to a central mill facility located at Mother Lode.

In the conceptual mine plans, 10-metre-high benches would be drilled and blasted, then loaded into 133 tonne haul trucks using 20 cubic metre front end loaders. At NBP, the haul trucks would deliver the mineralized material to either the stockpile transfer system for the mill grade mineralization or place the blasted material directly on the leach pad. The stockpile transfer system would consist of a grizzly, a feeder and conveyor belt feeding bins. Highway haul trucks would be loaded from the bin and transport the mill grade mineralization to the MLP mill stockpiles using Highway 95. Mill grade mineralization from MLP would also be stockpiled at the mill location. Mining rates at both NBP and MLP are sufficient to create a mill stockpile that will allow higher grade mineralization to be fed (grade streaming) to the mill in early years of the schedule. The mill stockpile is scheduled to reach a maximum size of 11.7 M tonnes by the end of year 2, and then begin to decline through the LOM.

The mine plan calls for an average total mining rate of 66 million (“M”) tonnes per year of combined overburden and mineralized material. Of that, an average of 30 M tonnes per year would be mineralized material placed on a heap leach pad at an average rate of 82 k tonnes per day. Another 3 M tonnes per year would be delivered to the mill at an average of 8,200 tonnes per day. The average overburden to mineralized material (strip ratio) would be 1.08. Based on this mining rate, the Project would have an active life of 9 years, with minor gold production for the additional 3-year rinse down period on the leach pad.


Processing Technologies

  • Gravity separation
  • Flotation
  • ROM/dump leach
  • Counter current decantation (CCD)
  • Concentrate leach
  • Pressure oxidation
  • Carbon in leach (CIL)
  • Carbon in column (CIC)
  • Carbon adsorption-desorption-recovery (ADR)
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Source

Summary:

The PROJECT Oxide materials will be processed in a standard heap leach recovery circuit commonly used in the region. The cyanide solutions from the heap leach will be treated in a Carbon-in-Columns (“CIC”) gold adsorption and desorption circuit.

The MLP mill will process NBP oxide, NBP sulphide and MLP sulphide materials separately from stockpiles. NBP Oxide material will be processed in a conventional gravity/CIL mill. Sulphide materials from both MLP and NBP will be processed through a milling and flotation plant to produce a concentrate. The flotation concentrate will be thickened, stockpiled, and processed through a pressure oxidation circuit followed by a CIL circuit. Oxide and sulphide CIL tails will be detoxified through an Inco/SO2 type process. Tailings will be pumped to a paste tailings thickener. Slurry will be deposited as a paste in a tailings facility. Detoxified, non-cyanide containing paste thickener overflow solution, will be returned to the mill.

Carbon from the CIC and CIL circuits will be processed in a carbon handling circuit located at the mill. The carbon handling will include carbon stripping, acid washing and reactivation circuits. The process solutions from carbon stripping will be sent to electrolytic cells for gold recovery in a precipitate sludge. The sludge will be retorted for mercury removal and then melted into doré bars in a furnace.

Recoveries & Grades:

CommodityParameterAvg. LOM
Gold Recovery Rate, % 78
Gold Head Grade, g/t  ......  Subscription required
Silver Head Grade, g/t 0.93
Subscription required - Subscription is required.

Projected Production:

CommodityUnitsAvg. AnnualLOM
Gold koz 2822,527
Silver koz  ......  Subscription required
Gold Equivalent koz  ......  Subscription required
All production numbers are expressed as metal in doré.

Operational Metrics:

Metrics
Stripping / waste ratio  ......  Subscription required
Daily ore mining rate  ......  Subscription required
Annual mining capacity  ......  Subscription required
Waste tonnes, LOM  ......  Subscription required
Ore tonnes mined, LOM  ......  Subscription required
Total tonnes mined, LOM  ......  Subscription required
Tonnes processed, LOM  ......  Subscription required
* According to 2018 study.
Subscription required - Subscription is required.

Reserves at September 18, 2018:

CategoryOreTypeTonnage CommodityGradeContained Metal
Measured Heap leach 34,560 kt Gold 0.27 g/t 305 koz
Measured Mill / Sulphide 9,311 kt Gold 1.59 g/t 475 koz
Measured Total 43,871 kt Gold 0.55 g/t 780 koz
Measured Heap leach 14,525 kt Silver 1.41 g/t 658 koz
Measured Mill / Sulphide 6,019 kt Silver 11.47 g/t 2,220 koz
Measured Total 20,544 kt Silver 4.36 g/t 2,878 koz
Indicated Heap leach 149,374 kt Gold 0.24 g/t 1,150 koz
Indicated Mill / Sulphide 18,249 kt Gold 1.68 g/t 988 koz
Indicated Total 167,623 kt Gold 0.4 g/t 2,138 koz
Indicated Heap leach 129,251 kt Silver 0.66 g/t 2,758 koz
Indicated Mill / Sulphide 8,315 kt Silver 8.93 g/t 2,388 koz
Indicated Total 137,566 kt Silver 1.16 g/t 5,146 koz
Measured & Indicated Heap leach 183,934 kt Gold 0.25 g/t 1,455 koz
Measured & Indicated Mill / Sulphide 27,560 kt Gold 1.65 g/t 1,463 koz
Measured & Indicated Total 211,494 kt Gold 0.43 g/t 2,918 koz
Measured & Indicated Heap leach 143,776 kt Silver 0.74 g/t 3,416 koz
Measured & Indicated Mill / Sulphide 14,334 kt Silver 9.99 g/t 4,608 koz
Measured & Indicated Total 158,110 kt Silver 1.58 g/t 8,024 koz
Inferred Heap leach 78,742 kt Gold 0.26 g/t 549 koz
Inferred Mill / Sulphide 2,284 kt Gold 1.61 g/t 118 koz
Inferred Total 81,026 kt Gold 0.26 g/t 667 koz
Inferred Heap leach 64,669 kt Silver 0.48 g/t 1,008 koz
Inferred Mill / Sulphide 116 kt Silver 9.12 g/t 34 koz
Inferred Total 64,785 kt Silver 0.5 g/t 1,042 koz

Commodity Production Costs:

CommodityUnitsAverage
Cash costs Gold USD  ......  Subscription required *
Total cash costs Gold Equivalent USD  ......  Subscription required *
All-in sustaining costs (AISC) Gold Equivalent USD  ......  Subscription required *
All-in sustaining costs (AISC) Gold USD  ......  Subscription required *
Assumed price Silver USD  ......  Subscription required *
Assumed price Gold USD  ......  Subscription required *
* According to 2018 study / presentation.
Subscription required - 'Investor' subscription is required.

Operating Costs:

Units2018
OP mining costs ($/t mined) USD 2.95 *
Processing costs ($/t milled) USD  ......  Subscription required
Total operating costs ($/t milled) USD  ......  Subscription required
* According to 2018 study.
Subscription required - 'Investor' subscription is required.

2018 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Initial CapEx $M USD 424
Sustaining CapEx $M USD  ......  Subscription required
Total CapEx $M USD  ......  Subscription required
Total OpEx $M USD  ......  Subscription required
Mining Taxes $M USD  ......  Subscription required
Income Taxes $M USD  ......  Subscription required
Gross revenue (LOM) $M USD  ......  Subscription required
Pre-tax Cash Flow (LOM) $M USD  ......  Subscription required
After-tax Cash Flow (LOM) $M USD  ......  Subscription required
Pre-tax NPV @ 5% $M USD  ......  Subscription required
After-tax NPV @ 5% $M USD  ......  Subscription required
After-tax NPV @ 10% $M USD  ......  Subscription required
After-tax NPV @ 7.5% $M USD  ......  Subscription required
Pre-tax IRR, %  ......  Subscription required
After-tax IRR, %  ......  Subscription required
After-tax payback period, years  ......  Subscription required
Subscription required - 'Investor' subscription is required.

Proposed Heavy Mobile Equipment as of September 18, 2018:
HME TypeSizeQuantity
Backhoe 3
....................... Subscription required 1
....................... Subscription required 4
....................... Subscription required 6
....................... Subscription required 3
....................... Subscription required 2
....................... Subscription required ....................... Subscription required 3
....................... Subscription required ....................... Subscription required 21
....................... Subscription required 2
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Feb 8, 2019
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2018
................................... Subscription required 2017
................................... Subscription required 2016
Subscription required - Subscription is required.

News:

NewsDate
Corvus Gold Expands Mother Lode Deposit Intersects New Deep Intrusive Zone Below Main Deposit with 50.3m @ 1.50 g/t Gold December 5, 2019
Corvus Gold Makes New Vein System Discovery at Cat Hill, North Bullfrog Project, Nevada October 23, 2019
Corvus Gold Inc. Closes C$23 Million Bought Deal Financing October 10, 2019
Corvus Gold Inc. Announces C$20 Million Bought Deal Financing October 2, 2019
Corvus Gold Ongoing Drill Program Continues to Expand Sierra Blanca Deposits to the West at North Bullfrog Project, Nevada September 23, 2019
Corvus Gold Closes $1.3M Private Placement Financing with AngloGold Ashanti (USA) Inc. at $2.60 per Share August 20, 2019
Corvus Gold Expands North Bullfrog’s Sierra Blanca Deposit to the West and North, Intersecting 16.8m @ 1.37 g/t Gold & 24.4m @ 1.21 g/t Gold and Stakes Land Package Adjacent to New Kinross Gold Claims August 6, 2019
Corvus Gold Expands Mother Lode Deposit to the North, Intersecting 48.8m @ 1.15 g/t Gold & 36.6m @ 1.59 g/t Gold, Defines New Style of Gold-Silver Mineralization June 11, 2019
Corvus Gold Expands Mother Lode Mineral Resource Potential to the West & Southwest, Drills 36.6m @ 2.03 g/t Gold & 25.9m @ 2.43 g/t Gold (including 18.3m @ 3.3 g/t) June 3, 2019
Corvus Gold Signs Private Placement Financing and Alaskan Royalty Sale Totalling $1.25M with EMX Royalty May 21, 2019
Corvus Gold: PEA Results for Combined North Bullfrog and Mother Lode Deposits, Nevada November 1, 2018

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