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Paramount Gold’s Feasibility Study Confirms Economic Viability of the Proposed Grassy Mountain Gold Mine With an After-Tax NPV of $105 Million

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Paramount Gold’s Feasibility Study Confirms Economic Viability of the Proposed Grassy Mountain Gold Mine With an After-Tax NPV of $105 Million






Paramount Gold Nevada Corp. (NYSE American: PZG) released the results of the Feasibility Study for its 100% owned Grassy Mountain Gold Project in eastern Oregon. The Study outlines an underground mining operation with exceptional economic viability yielding strong NPV and IRR results, low initial capital and low all-in sustaining costs that generate substantial cash-flows over the life of mine. The Study will be filed on SEDAR within 45 days of this news release.


The base case was conducted using two-year trailing gold and silver prices per ounce of $1,472 and $16.96 respectively.


The highlights of the NI 43-101 Technical Report in the base case scenario are as follows:


  • Pre-tax IRR of 27.9% and NPV5% of $123M which increase significantly to 44.7% and $238M at $1,900 gold;
  • After-tax IRR of 26.0% and NPV5% of $105M which increase significantly to 40.9% and $195M at $1,900 gold;
  • Life of mine cash costs of $5831 and AISC of $6712 per ounce of gold3;
  • Initial CapEx of $97.5M includes $10.1M of estimated contingencies, $25.6M of sustaining CapEx and $6.3M closure costs for a 750 tpd mine and milling operation;
  • Initial 8 year mine life producing 362,000 ounces of gold and 425,000 ounces silver;
  • Annual production of 47,000 ounces of gold and 55,000 ounces of silver;
  • Exceptional average gold and silver recoveries of 92.8% and 73.5 % respectively;
  • After-tax payback of 3.1 years; and
  • Total free cash flow of $165M (post-tax);


“This study is everything we had hoped for, including important improvements over the preliminary feasibility study we completed a little over two years ago. Paramount can now satisfy the remaining permitting requirements identified by the State of Oregon and the Bureau of Land Management in Paramount’s recently submitted Consolidated Permit Application and Plan of Operation. We are very close to realizing our goal of building Grassy Mountain into a modern and environmentally friendly mine, leveraging the industry’s best practices and technologies,” stated Glen Van Treek, the Company’s President and COO. ”Our focus now is to add resources to extend mine life and generate further economic returns for our shareholders,” he said.


The FS was completed by a group of industry leading consulting firms led by: Ausenco Engineering Canada Inc. who managed the overall study and were responsible for processing and infrastructure design and oversaw metallurgical testing; Mine Development Associates who updated the mineral resource estimate and completed the mine planning and reserves estimation; Golder Associates who designed the tailings storage facility; and EM Strategies who oversaw all environmental aspects of the Feasibility Study.


Paramount’s CEO, Rachel Goldman added: “Since acquiring Grassy Mountain in 2016, the Company has been committed to building a profitable mine with a quick payback. The results of the Feasibility Study confirm our goal is achievable, validating the hard work that the team has dedicated towards advancing Grassy to become Oregon’s first gold mine, and giving us a first-mover advantage in the state.”


Mineral Resources


Mineralized material is reported under the Canadian Institute of Mining standards for reporting mineralized material. Grassy Mountain’s “in-pit mineralization” was estimated using GEOVIA Whittle software to define all potentially economic mineralization that could be mined from surface in an open pit configuration. The primary parameters entered by MDA for the in-pit constrained resources, which comprise more than 99% of the total mineral resources, include $1,500/oz of gold and $20/oz of silver (typical of industry resource reporting), a 5,000 ton per day processing rate using a $2.00 per ton mining cost, $13 per ton processing cost, and average gold and silver recoveries of 80% and 60% respectively. Processing is assumed to consist of crushing and milling followed by Carbon in Leach recovery resulting in the production of a DORE bar on site. In-pit and underground mineral resources are tabulated as follows:




Imperial Units          
Classification Tons Au
Measured 18,190,000 0.020 0.079 369,000 1,438,000
Indicated 12,712,000 0.054 0.146 691,000 1,861,000
Measured + Indicated 30,902,000 0.034 0.107 1,060,000 3,299,000
Inferred 1,004,000 0.041 0.120 41,000 120,000




Metric Units          
Classification Tonnes Au
Measured 16,502,000 0.69 2.71 369,000 1,438,000
Indicated 11,532,000 1.85 5.01 691,000 1,861,000
Measured + Indicated 28,034,000 1.17 3.67 1,060,000 3,299,000
Inferred 911,000 1.41 4.11 41,000 120,000


  1. Mineral resources are comprised of all model blocks at a 0.012 oz AuEq/ton cutoff that lie within an optimized pit plus blocks at a 0.060 oz AuEq/ton cutoff that lie outside of the optimized pit;
  2. oz AuEq/ton (gold equivalent grade) = oz Au/ton + (oz Ag/ton ÷ 100);
  3. The mineral resources are inclusive of the mineral reserves;
  4. Mineral resources that are not mineral reserves do not have demonstrated economic viability;
  5. The Effective Date of the Grassy Mountain resource estimate is March 31, 2020; and
  6. Rounding may result in apparent discrepancies between tons/tonnes, grade, and contained metal content.


Mineral Reserves


Proven and probable mineral reserves are reported using CIM standards and were based on all defined parameters in the FS using measured and indicated resources. Reserves are estimated for an underground mining operation with defined portal access and decline development to access the mineralized material. Initial economic material was defined using various stope sizes with an initial cut-off grade of 0.1 ounces of gold per ton.


Reserves are reported using measured and indicated resources inside the defined economically viable mining stopes, including ore lost and dilution from measured and indicated resources.




Imperial Units
Classification Tons Au
Proven 259,554 0.18 0.26 46,987 68,421
Probable 1,651,894 0.20 0.29 333,036 485,522
Proven + Probable 1,911,448 0.20 0.29 380,023 553,943
Ore Loss & Dilution 158,640 0.06 0.15 9,910 24,336
Proven + Probable + Ore Loss & Dilution 2,070,088 0.19 0.28 389,933 578,279



Metric Units
Classification Tonnes Au
Proven 235,463 6.21 9.04 46,987 68,421
Probable 1,498,573 6.91 10.08 333,036 485,522
Proven + Probable 1,734,036 6.82 9.94 380,023 553,943
Ore Loss & Dilution 143,916 2.14 5.26 9,910 24,336
Proven + Probable + Ore Loss & Dilution 1,877,952 6.46 9.58 389,933 578,279


Mine Plan and Production


The mine plan was developed using a drift and fill underhand mining methodology. A cut-off grade of 0.1 opt Au was used to define economic stopes. Ore processing from the upper portion of the mine is expected to commence concurrently with the completion of the processing plant and infrastructure. Following ramp up, the mine is expected to produce an average of 1,300 to 1,400 tonnes per day, 4 days a week, which will provide enough material for the 750 ton per day mill and processing plant to operate at full capacity for 7 days a week.


Below is a summarized mine plan on a year by year basis over the life of the mine.



YEAR 1 2 3 4 5 6 7 8 Total
Mined M&I Resource Above (COG)                  
Tons (t)   158,166   203,485   197,545   201,166   204,796   235,360   205,313   125,678    1,531,510
Grade (oz Au/ton)         0.26         0.22         0.23         0.26         0.22         0.22         0.22         0.24              0.23
Ounces (oz Au)     41,670     44,190     46,132     52,931     44,597     51,345     44,655     30,111       355,631
Grade (oz Ag/ton)         0.35         0.28         0.29         0.33         0.32         0.30         0.32         0.34              0.31
Ounces (oz Ag)     55,827     57,405     56,793     66,262     65,763     71,156     65,157     43,109       481,473
Mined M&I Resource Subgrade                  
Tons (t)     51,620     61,317     51,369     59,088     55,378     45,357     37,085     18,724       379,938
Grade (oz Au/ton)         0.06         0.06         0.06         0.06         0.07         0.07         0.07         0.07              0.06
Ounces (oz Au)       3,159       3,887       3,234       3,597       3,646       3,046       2,504       1,319         24,392
Grade (oz Ag/ton)         0.21         0.18         0.17         0.18         0.19         0.20         0.21         0.20              0.19
Ounces (oz Ag)     10,902     10,832       8,770     10,922     10,603       9,148       7,641       3,651         72,469
Total Mined to Stockpile                  
Tons (t)   209,786   264,802   248,913   260,254   260,175   280,717   242,398   144,402    1,911,447
Grade (oz Au/ton)         0.21         0.18         0.20         0.22         0.19         0.19         0.19         0.22              0.20
Ounces (oz Au)     44,829     48,077     49,366     56,527     48,243     54,391     47,159     31,430       380,023
Grade (oz Ag/ton)         0.32         0.26         0.26         0.30         0.29         0.29         0.30         0.32              0.29
Ounces (oz Ag)     66,729     68,237     65,563     77,184     76,367     80,305     72,798     46,761       553,943
Total with Ore Loss & Dilution                  
Tons (t)   229,597   288,356   266,720   280,963   278,486   304,308   265,800   155,858    2,070,088
Grade (oz Au/ton)         0.20         0.17         0.19         0.21         0.18         0.18         0.18         0.21              0.19
Ounces (oz Au)     45,921     49,568     50,575     57,830     49,528     55,845     48,498     32,167       389,933
Grade (oz Ag/ton)         0.30         0.25         0.26         0.29         0.29         0.28         0.29         0.31              0.28
Ounces (oz Ag)     69,602     71,419     68,220     80,221     79,660     84,131     76,294     48,731       578,279


Metallurgy and Process


Ausenco’s metallurgists and process design engineers evaluated and reviewed extensively the previously completed metallurgical testing and conducted additional testing for recovery and grindability, leach time and cyanide concentration, amongst other parameters. The Grassy mountain processing facility will consist of a milling facility followed by a CIL circuit. Ausenco provided a recovery relationship between grade and recovery based on all tests conducted, which was used to estimate recovery on a monthly basis for the mine plan, the overall average gold and silver recoveries estimated are 92.8% for gold and 73.5 % for silver.


Capital Costs


Grassy Mountain is located on both private and federal land. Existing road access will be upgraded to handle additional use from mine development and operation. As an alternative to on-site diesel power generation, renewable electricity will be provided by Idaho Power, from the Hope substation in Malheur County, through the construction of a power line that will bring power to site. Tailings disposal during the life of mine will be constructed in three stages, however a total of four stages have been designed to accommodate for potential mine life expansion whereby additional ore will be processed. The processing plant will consist of a crushing and mill facility, followed by CIL processing of the mill fines resulting in a mill processing design capacity of 750 tons per day. Capital costs were estimated using all new equipment. Substantial savings in capital could be achieved by sourcing used equipment which is plentiful in the western U.S.


The capital costs are highlighted in the following table:



(000’s of $US)
(000’s of $US)
(000’s of $US)
Mine 10,700 15,000 25,700
Site Development 4,000   4,000
Plant 23,400   23,400
Mineral Processing   300 300
Process Indirect 14,300   14,300
On-site Infrastructure 12,200 700 12,900
Off-site Infrastructure 9,100 400 9,500
Tailing Storage Facility 6,000 14,600 20,600
Owners Capital 7,700 (5,600) 2,100
Subtotal 87,500 25,600 113,000
Contingency 10,100   10,100
Total Capital 97,500 25,600 123,100
Closure Costs     6,300

*Rounding may cause discrepancies


Operating Costs


The exceptional location of Grassy Mountain and the geometric nature of the deposit’s mineralization are major factors in the low processing cost as outlined in the Feasibility Study. Grassy is in close proximity to the towns of Vale and Ontario in Oregon which contributes to lower labour costs; it is just 60 miles south of the project’s cement source, Ash Grove’s cement plant in Durkee, Oregon; the mine is less than 20 miles from Idaho Power’s, hydroelectrical power substation, which will attribute a low power cost of 6 cents per kwh; the dissemination of the deposit allows for a very low waste to ore ratio; and a majority of the development was designed within the ore body or in slightly lower grade material that will be processed creating incremental revenue. These features will help Grassy deliver US gold-industry leading operating costs of $100 per ton of ore processed.


Processing cost over the life of mine are estimated at $57.5 million or $27.77 per ton of ore processed. These costs are outlined in detail as follows:



Cost Item Total Costs
(000’s of $/year)
Total Costs
Mill Feed
Fixed Costs      
Labor  3,245 42.7 % 11.9
General Maintenance 1,060 13.9 % 3.9
Sub-total (Fixed Costs) 4,305 56.6 % 15.73
Variable Costs      
Power 1,142 15.0 % 4.2
Reagents & Operating Consumables 1.945 25.6 % 7.1
Maintenance Consumables 210 2.8 % 0.8
Sub-total (Variable Costs) 3,297 43.4 % 12.04
TOTAL 7,602 100 % 27.77


Note: Process cost only. Rounding may cause apparent discrepancies.


Total mining operating costs over the life of mine are estimated at $120.5 million. Total general and administration costs are estimated at $29.9 million ($3.73 M/Year), resulting in $72.65 per processed ton of mining cost.



Operating Cost Item

Total Costs Total cost Mill feed
(000’s of $/Year) % $/t
Blasting 35 0.2% $       0.14
Blasting Product 1,251 6.7% $       4.83
Dual (Drill & Bolt) Operating 436 2.3% $       1.68
Dual (Drill & Bolt) Product Operating 1,112 5.9% $       4.30
Mucking 592 3.1% $       2.29
Shotcrete 49 0.3% $       0.19
Transmixer 56 0.3% $       0.22
Trucking 524 2.8% $       2.03
Trucking CRF (Backfill) 199 1.1% $       0.77
Backfill Product 3,481 18.5% $     13.45
Subtotal Mining Operating Cost 7,735 41.1% $      29.90
Labor 6,471 34.4% $      25.01
Electrical 329 1.8% $        1.27
Diesel Fuel 435 2.3% $        1.68
General Supplies 97 0.5% $        0.37
Total General Operating Cost 7,332 39.0% $      28.33
TOTAL OPERATING (Mining + General) 15,067 80.1% $      58.23
General and Administration 3,732 19.9% $      14.42
Total Mine and G&A 18,799 100% $     72.65


Economic Analysis


A base case for the economic analysis was performed at gold and silver prices per ounce of $1,472 and $16.96 respectively. The base case scenario provides a post-tax IRR of 26.0 % and a NPV5% of $105 million. The break-even gold price for this mining operation is approximately $1,000 per ounce of gold.


The following table illustrates the sensitivities that a variety of gold price environments have on both the NPV and IRR:



  Base Case Upside Case Lower Case
Gold Price ($/oz) 1,472 1,900 1,300
Silver Price ($/oz) 16.96 16.96 16.96
Cash Operating Cost Per Au Ounce 1 $583 $590 $581
Total Cost Per Ounce Au (AISC )1 $671 $678 $669
After-tax Internal Rate of Return 26.0% 40.9% 19.2%
After-tax Net Present Value (5%) (000’s of USD’s) $105 $195 $69
After-tax Net Present Value (8%) (000’s of USD’s) $79 $156 $48
After-tax Net Present Value (10%) (000’s of USD’s) $65 $134 $36
Payback from start of production (years) 3.1 2.0 3.7

1 After silver credits


Methods and Parameters Relevant to the Resource Estimation


The gold and silver mineral resources at Grassy Mountain were modeled and estimated using the following criteria:


  • statistically evaluating the drill data;
  • separately interpreting gold and silver mineral domains on a set of 070°-looking cross sections spaced at 50-foot intervals;
  • rectifying the cross-sectional mineral-domain interpretations on level plans spaced at 10-foot vertical intervals and using these plans to code a block model;
  • analyzing the modeled mineralization spatially and statistically to aid in the establishment of estimation and classification parameters; and
  • interpolating grades into the block model using the coding of the level-plan gold and silver mineral domains to constrain the estimation.


Resources with a reasonable expectation of potential extraction by open-pit methods are constrained to lie within an optimized pit. Additional parameters used in the optimization to those provided above include a general administrative cost of $2.22 per ton processed and a refining cost of $5.00 per ounce produced. The in-pit resources were then tabulated by the application of a gold-equivalent cut-off of 0.012 opt. The gold-equivalent grades were determined using a gold to silver ratio of a 100 to 1.


The effective date of the mineral resources and mineral reserves is March 31, 2020.


NI 43-101 Disclosure


The metallurgical analysis, process design development of the process plant capital and operating cost estimates and financial modeling were supervised and reviewed by Tommaso Roberto Raponi of Ausenco, a Qualified Person (as defined under National Instrument 43-101) and is independent of Paramount Gold Nevada Corp. 


The mineral reserve estimate was estimated by Joseph Seamons PE, from MDA, a Division of RESPEC, a Qualified Person (as defined under National Instrument 43-101) and is independent of Paramount Gold Nevada Corp. 


The mineral resource estimate was completed and reviewed by Michael Gustin of MDA, a Division of RESPEC, a Qualified Person (as defined under National Instrument 43-101) and is independent of Paramount Gold Nevada Corp.


All the above-named Qualified Persons have reviewed and approved this news release.


About Paramount Gold Nevada Corp.


Paramount Gold Nevada Corp. is a U.S. based precious metals exploration and development company. Paramount’s strategy is to create shareholder value through exploring and developing its mineral properties and to realize this value for its shareholders in three ways: by selling its assets to established producers; entering into joint ventures with producers for construction and operation; or constructing and operating mines for its own account.


Paramount owns 100% of the Grassy Mountain Gold Project which consists of approximately 11,000 acres located on private and BLM land in Malheur County, Oregon. The Grassy Mountain Gold Project contains a gold-silver deposit (100% located on private land) for which results of a positive Pre-Feasibility Study have been released and key permitting milestones accomplished.


Paramount owns a 100% interest in the Sleeper Gold Project located in Northern Nevada, the world’s premier mining jurisdiction. The Sleeper Gold Project, which includes the former producing Sleeper mine, totals 2,322 unpatented mining claims (approximately 60 square miles or 15,500 hectares). The Sleeper gold project is host to a large gold deposit (over 4 million ounces of mineralized material) and the Company has completed and released a positive Preliminary Economic Assessment.


About Ausenco


Ausenco is a global diversified engineering, construction and project management company providing consulting, project delivery and asset management solutions to the resources, energy and infrastructure sectors. Ausenco’s experience in gold and silver projects ranges from conceptual, pre-feasibility and feasibility studies for new project developments to project execution with EPCM and EPC delivery. Ausenco is currently engaged on a number of global projects with similar characteristics and opportunities to the Grassy Mountain Gold Project.


Posted September 15, 2020

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