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United States
Grassy Mountain Project

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 Location:
92 km W from Boise, Oregon, United States

  Project Contacts:
665 Anderson Street
Winnemucca
Nevada, United States
89445
Fax775-625-9881
EmailEmail
WebsiteWeb
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Overview

StagePermitting
Mine TypeUnderground
Commodities
  • Gold
  • Silver
Mining Method
  • Mechanized Cut & Fill
  • Cemented backfill
Mine Life7.8 years (as of Jan 1, 2022)


Owners

Source: p. 30,50
CompanyInterestOwnership
Paramount Gold Nevada Corp. 100 % Indirect
Paramount’s 100% ownership of the Grassy Mountain project is subject to underlying agreements and royalties. Paramount holds its Project interest through an indirectly wholly owned subsidiary, Calico Resources USA Corp. (Calico).

Contractors

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Deposit Type

  • Breccia pipe / Stockwork
  • Epithermal
  • Vein / narrow vein


Summary:

The geological setting, hydrothermal alteration, styles of gold-silver mineralization, and close spatial and timing association with silica sinter deposition, indicate that Grassy Mountain is an example of the hot-springs subtype of low-sulfidation, epithermal precious-metals deposits. The Grassy Mountain deposit is characterized by stacked sinter terraces that demonstrate hydrothermal fluids vented at the paleosurface concurrent with lacustrine and intermittent fluvial sedimentation.

The Grassy Mountain gold–silver deposit is located largely within the silicic and potassic alteration, zones, beginning approximately 200 ft below the surface. The deposit has extents of 1,900 ft along a N60°E to N70°E axis, as much as 2,700 ft in a northwest-southeast direction, and as much as 1,240 ft vertically. The surface expression of the mineralization is indicated by weak to moderately strong silicification and iron-staining, accompanied by scattered, 1/8- to 1.0-inch wide creamy to light-gray chalcedonic veins that filled joints.

The deposit consists of a central higher-grade core with gold grades of >~0.03 oz/ton Au that is surrounded by a broad envelope of lower-grade mineralization. The central higher-grade core is almost 1,000 ft long on the N60°E to N70°E axis, by 450 ft in width and 450 ft in vertical extent, all of which is above the Kern Basin Tuff and below a distinctive sinter unit.

Central Higher-Grade Core Zone
Three distinct and overla ........


Mining Methods

  • Mechanized Cut & Fill
  • Cemented backfill


Summary:

The mine design was based on an average production rate of 1,200 tons per day using a four-day-on and three-day-off schedule, with two 12-hour shifts per day, to provide 24-hour coverage during the four operating days at full operation. This will provide sufficient material to feed 750 tons/d to the mill on a seven day per week basis.

The mining cycle involves drilling, blasting, and mucking for the development and production access. The final part of the mining cycle is to backfill the stopes.

The Grassy Mountain mine will be an underground operation accessed via one decline and a system of internal ramps. One ventilation raise is included in the design to be used for ventilation and secondary egress. The mechanized cut-and-fill mining method was selected. The mining direction will be underhand. Cemented rock fill (CRF) will be used for backfill. The mechanized cut-and-fill method is highly flexible and can achieve high recovery rates in deposits with complex geometries, as is the case at the Grassy Mountain deposit. The estimated mine life is eight years.

The mining sequence contains a detailed level sequence and an underhand sequence. The level access is mined first. The mains are mined second. Typically, two mains are mined at the same time providing multiple mining locations on a level. After the mains are mined, then the production drifts can begin mining. The production drifts are sequenced with primaries and secondaries. The primaries ........


Crushing and Grinding
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Processing

Flow Sheet: Subscription required

Summary:

- subscription is required.


Projected Production:

CommodityProductUnitsAvg. AnnualLOM
Gold Payable metal koz 361
Gold Metal in doré koz 47362
Silver Payable metal koz  ......  Subscription required
Silver Metal in doré koz  ......  Subscription required  ......  Subscription required
Gold Equivalent Metal in doré koz  ......  Subscription required
Gold Equivalent Payable metal koz  ......  Subscription required

Operational Metrics:

Metrics
Daily milling rate  ......  Subscription required
Daily ore mining rate  ......  Subscription required
Waste tonnes, LOM  ......  Subscription required
Ore tonnes mined, LOM  ......  Subscription required
Tonnes milled, LOM  ......  Subscription required
Annual milling rate  ......  Subscription required
* According to 2022 study.
Subscription required - Subscription is required.

Reserves at June 30, 2022:
Mineral Reserves are reported inside stope designs assuming drift-and-fill mining methods, and an economic gold equivalent cutoff grade of 0.10 oz/ton AuEq.
Mineral Resources comprised all model blocks at a 0.011 oz/ton AuEq cut-off that lie within an optimized pit plus blocks at a 0.085 oz/ton AuEq cut-off that lie outside of the optimized pit.

CategoryTonnage CommodityGradeContained Metal
Proven 259,600 tons Gold 0.181 oz/ton
Proven 259,600 tons Silver 0.264 oz/ton
Probable 1,651,900 tons Gold 0.202 oz/ton
Probable 1,651,900 tons Silver 0.294 oz/ton
Proven & Probable 1,911,400 tons Gold 0.199 oz/ton
Proven & Probable 1,911,400 tons Silver 0.29 oz/ton
Measured 21,153,000 tons Gold 0.017 oz/ton 363,000 oz
Measured 21,153,000 tons Silver 0.072 oz/ton 1,529,000 oz
Indicated 12,902,000 tons Gold 0.03 oz/ton 392,000 oz
Indicated 12,902,000 tons Silver 0.115 oz/ton 1,480,000 oz
Measured & Indicated 34,055,000 tons Gold 0.022 oz/ton 755,000 oz
Measured & Indicated 34,055,000 tons Silver 0.088 oz/ton 3,009,000 oz
Inferred 1,151,000 tons Gold 0.037 oz/ton 42,000 oz
Inferred 1,151,000 tons Silver 0.109 oz/ton 126,000 oz

Commodity Production Costs:

CommodityUnitsAverage
Total cash costs Gold USD  ......  Subscription required *†
All-in sustaining costs (AISC) Gold USD  ......  Subscription required *†
Assumed price Silver USD  ......  Subscription required&nbs
Assumed price Gold USD  ......  Subscription required&nbs
* According to 2022 study / presentation.
† Net of By-Product.
Subscription required - Subscription is required.

Operating Costs:

Units2022
UG mining costs ($/ton milled) USD 67.3 *
Processing costs ($/ton milled) USD  ......  Subscription required
G&A ($/ton milled) USD  ......  Subscription required
Total operating costs ($/ton milled) USD  ......  Subscription required
* According to 2022 study.
Subscription required - Subscription is required.

2022 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Initial CapEx $M USD  ......  Subscription required
Sustaining CapEx $M USD  ......  Subscription required
Closure costs $M USD  ......  Subscription required
Total CapEx $M USD  ......  Subscription required
UG OpEx $M USD  ......  Subscription required
Processing OpEx $M USD 70.2
Refining costs $M USD  ......  Subscription required
G&A costs $M USD 34.3
Total OpEx $M USD  ......  Subscription required
Income Taxes $M USD  ......  Subscription required
Royalty payments $M USD  ......  Subscription required
Gross revenue (LOM) $M USD  ......  Subscription required
EBITDA (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
Pre-tax IRR, %  ......  Subscription required
After-tax IRR, %  ......  Subscription required
Pre-tax payback period, years  ......  Subscription required
After-tax payback period, years  ......  Subscription required
Subscription required - Subscription is required.


Proposed Heavy Mobile Equipment as of June 30, 2022:
HME TypeModelSizeQuantityLeased or
Contractor
ANFO Loader ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required
....................... Subscription required ....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
....................... Subscription required ....................... Subscription required ....................... Subscription required Leased
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Nov 25, 2022
....................... Subscription required ....................... Subscription required Subscription required Nov 25, 2022
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
Feasibility Study Report 2022
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2020
................................... Subscription required 2019
Press Release 2018
Year-end Mineral Reserves 2017
Preliminary Economic Assessment 2015
Subscription required - Subscription is required.

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