Heliostar Announces Positive Prefeasibility Study for Cerro del Gallo with Significant Expansion Potential Company Highlights:
TSX.V: HSTR
OTCQX: HSTXF
Heliostar Announces Positive Prefeasibility Study for Cerro del
Gallo with Significant Expansion Potential
Company Highlights:
• Base Case shows US$424M post tax NPV5, 33.1% IRR, with a 2.3 year payback at a US$2,300/oz gold
price
• Upside Case shows US$972M post tax NPV5, 59.3% IRR, with a 1.4 year payback at a US$3,900/oz
gold price
• 1.31M GEOs produced over a 15.3 year mine life, averaging approximately 85,700 GEOs/yr (94,000
GEOs/yr over Years 1-5) at a co-product AISC of US$1,390/GEO
• Initial capital expenditure of US$195.3M for an open pit, heap leach mine and SART plant, including
owner’s costs, contingency and initial working capital requirements
• Average annual free cash flow of US$47.6M at $2,300/oz gold price (US$104.5 at $3,900/oz) driven
by 0.73 g/t AuEq life of mine head grade, low strip ratio (0.3:1) and low sustaining capital
• Indicated resource of 240Mt grading 0.63 g/t AuEq for 4.9M GEOs (0.38g/t gold, 13.78g/t silver,
0.10% copper), and an Inferred resource of 24Mt grading 0.52 g/t AuEq for 0.4M GEOs (0.28g/t gold,
13.67g/t silver, 0.09% copper), providing significant upside opportunities if property boundary
constraints lifted
Vancouver, Canada, December 11, 2025 – Heliostar Metals Ltd. (TSX.V: HSTR, OTCQX: HSTXF, FRA: RGG1)
(“Heliostar” or the “ Company”) is pleased to announce strong economics in an updated Pre feasibility Study
(“PFS”) for its 100% owned Cerro del Gallo project located in the state of Guanajuato, Mexico.
Heliostar CEO, Charles Funk, commented, “The Cerro del Gallo Pre feasibility Study demonstrates a mine that
fits perfectly with Heliostar’s growth trajectory to larger, lower cost operations. The project has low CAPEX,
shows strong free cash flow at a conservative gold price and significant resource upside. With this study the
value of Cerro del Gallo to Heliostar has now been established, having been delayed due to our initial focus on
operations following the acquisition of the mines and properties in November 2024. This study confirms Cerro
del Gallo as an important development project in the Heliostar portfolio, and the Company plans to continue
technical work, permitting and community engagement to advance the project to a feasibility level. Organic
growth from Ana Paula first, and later from Cerro del Gallo, is planned to launch Heliostar to 300,000 ounces
of annual gold equivalent production by the end of the decade.
The technical report supporting this news release will be available on SEDAR+ (www.sedarplus.ca) and on the
Company's website (www.heliostarmetals.com) within the next 45 days. The Cerro del Gallo technical report
that is the subject of this news release will use United States dollars (USD or US$) unless otherwise noted.
Cerro del Gallo Prefeasibility Study Overview
The Prefeasibility Study is based on the current reserve base of 2.27M GEOs of Probable Mineral Reserves as
shown in the Mineral Reserves Update effective July 31, 2025.
The study outlines a 15.3 year mine life, producing 85,700 koz gold equivalent ounces (“GEOs”) per year at an
average total cash cost of $1,252/GEO and an all-in sustaining cost (AISC) of $1,390 GEO, and costing $195.3M
in initial capital expenditures (“CAPEX”) to bring into production. At the base case gold pric e of $2,300 per
ounce, this results in an after-tax NPV of $424M, an IRR of 33.1% and a payback period of 2.3 years.
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The Cerro del Gallo project is envisaged as a 6 million tonne -per-year open -pit mining operation using
conventional drill, blast, load, and haul methods, with mining activities performed by a contractor -supplied
fleet. Ore will be crushed using a multi-stage crushing circuit, including conventional crushing and High Pressure
Grinding Roll (“HPGR”), and stacked on a lined heap-leach pad. Leaching will use conventional cyanide solution
application. Pregnant solution will be processed through an adsorption, desorption and recovery (“ADR”)
circuit for gold recovery, producing gold doré on-site. Copper and silver dissolved in solution will be recovered
through a sulphidization, acidification, recycling, and thickening (“SART”) circuit and shipped to smelters.
A dedicated waste rock storage facility will be located adjacent to the open pit, sized according to life-of-mine
requirements, with engineered drainage and environmental controls. Processing residues will consist primarily
of leached material on the heap-leach pad; therefore, no conventional tailings storage facility will be required.
Site infrastructure will include an upgraded connection to the national power grid, a reliable water supply from
permitted local wells, and supporting buildings such as a maintenance shop, warehouse, administration offices,
security facilities, and expanded camp accommodations for operational staff.
Key Highlights
Forecast Production Highlights
Ore Feed 6,000 Ktpa
Strip Ratio 0.32:1 W:O
Grade – LOM 0.73 g/t AuEq
Grade – Years 1-5 0.80 g/t AuEq
Life of Mine Produced 1,310 Koz GEO
Processing Rate 16,438 Tpd
Process Recovery (Gold / Silver / Copper) 59.4 / 49.3 / 61.8 %
Life of Mine 15.3 Years
Annual Production - LOM 85.7 Koz GEO
Annual Production – Years 1-5 94.2 Koz GEO
Forecast Financial Highlights
Average Cash Costs (US$ per GEO) 1 $1,252 /oz
Average AISC (US$ per GEO) 1 $1,390 /oz
Total Initial Capital Cost $195.3 M
Total Sustainable Capital Cost $160.3 M
Total Life of Mine Capital Cost 2 $355.6 M
1. Non-International Financial Reporting Standards (IFRS) measures. All-in sustaining costs (AISC) were first issued by the World Gold Council
(WGC) in 2013 with an updated Guidance note issued in 2018.
2. Includes US$132.0 million reclamation expenditure at the end of the mine life.
Forecast Return Estimates based on Gold Price 1, 2
US$2,300/oz 3 US$3,900/oz 4
IRR 33.1% 59.3%
NPV @ 5% discount $423.9M $972.4M
Payback 2.3 years 1.4 years
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1. All other key parameters set at base assumptions, including the 5% discount rate used. More detailed analysis will be presented
in the full technical report.
2. After tax return estimates.
3. Base gold price assumption used in the technical report.
4. Comparison gold price of US$3, 900 with reference to US$4,198 London Bullion Market Association (LBMA) PM gold price on
trading day December 9, 2025.
Figure 1 – Isometric View of Cerro del Gallo Resource with Reserve Pit Shell
Figure 2 – Cross Section through Cerro del Gallo Resource with Reserve Pit Shell
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Forecast Operating Cost Estimates
Operating costs at the Cerro del Gallo Project will benefit from the simplicity of a truck and shovel open pit
mine, very low strip ratio, and access to low -cost grid power and regional infrastructure. The crush–
agglomerate–heap-leach–ADR–SART flowsheet utilizes industry standard equipment and p rocesses. It
supports efficient processing of the Cerro del Gallo ore with moderate reagent use and no requirement for
milling or conventional tailings storage.
Estimations of total cash costs average US$1,252/GEO, with AISC of US$1,390/GEO over the 15.3 -year mine
life. Revenue credits from copper and silver recovered through the SART circuit further strengthen operating
margins and contribute to a robust, long-life cost profile.
Total Operating Cost Summary
Operating Costs Operating Cost
(US$/GEO)
Operating Cost
(US$/t ore)
Total mining $274.02 $3.79
Total processing $658.44 $9.12
Total site general and administrative $65.61 $0.91
Smelter, Refinery and Transport $68.55 $0.95
Cash operating costs $1,066.62 $14.77
Production taxes $80.29 $1.11
Royalties $105.12 $1.46
Total cash costs $1,252.03 $17.33
Sustaining capital costs $138.2 $1.91
Total AISC $1,390.23 $19.25
Forecast Capital Cost Estimates
The initial capital cost for the project is estimated to be $195.3M including $15.6M for initial working capital
(60 days) and $22.3M in total contingency. The total initial required capital expenditure will benefit from
proximity to infrastructure and the assumption of a contractor -supplied fleet. Sustaining capital costs are
primarily related to completion of a powerline to the site and three leach pad expansions. The cost estimate is
based on more advanced work that will progress into a feasibility study, however, it includes a contingency of
17.5% of the total cost.
The Company’s LOM plan allocates US$132.0M for reclamation work at the end of the mine life.
Forecast Capital Cost Summary
Capital Costs Initial
(US$M)
Sustaining
(US$M)
Total LOM
(US$M)
Mining Costs $1.4 - $1.4
Mobile Equipment $3.9 - $3.9
Site & Utilities General $10.2 - $10.2
Power Generation & Site Distribution $11.0 - $11.0
Crushing Circuit $28.8 - $28.8
Agglomeration $4.9 - $4.9
Stacking System $6.8 - $6.8
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Heap Leach Solution $21.1 - $21.1
SART Plant $20.3 - $20.3
Recovery Plant $13.3 $35.1 $48.4
Reagents $2.5 - $2.5
Laboratory $2.9 - $2.9
Total direct costs $127.2 $35.1 $162.3
Spare Parts $5.7 - $5.7
Initial Fills $0.9 $0.9
Contingency $22.1 $8.8 $30.9
Indirect Costs $6.5 - $6.5
Other Owner’s Costs $3.6 - $3.6
EPCM $13.8 - $13.8
Working Capital (60 days) $15.6 -$15.6 -
Closure and reclamation - $132.0 $132.0
Total indirect costs $68.2 $125.2 $193.4
Total Costs (excluding IVA) $195.3 $160.3 $355.6
Economic Analysis
The economic analysis shows a base case after -tax net present value at a discount rate of 5% of US$423.9M,
an after -tax internal rate of return of 33.1%, and a payback period of 2.3 years at US$2,300/oz gold. The
projected mine life is 15.3 years in the PFS. Approximately 1,310k GEOs (888 koz gold, 22.2 Moz silver and 59
kT copper) are projected to be produced and sold over the life of the mine.
Summary Economic Results
Project Valuation Overview Units After Tax Before Tax
Total cash flow US$ M $724.1 $1,166.9
Average annual cash flow US$ M $47.6 $76.3
Average annual cash flow – Years 1-5 US$ M $77.6 $104.7
NPV @ 5.0% (base case) US$ M $423.9 $699.4
Internal rate of return % 33.1% 44.9%
Payback period Years 2.3 1.8
Payback multiple x 4.4 6.5
Metal Prices
The gold market has experienced significant upward price movement in the past few years. The gold price at
the effective date of the technical report is about 83% above the base case gold price used in the study.
The sensitivity analysis presents gold price scenarios up to US$4,100/gold ounce (near spot prices) to
understand the potential impact of continued gold price movements. From the base case price of $2,300/oz, a
change in the average gold price of 10% (US$2 30/gold ounce) would change the after -tax NPV 5% by
approximately US$76.2M.
The economics of the Pre feasibility Study are most sensitive to changes in gold price and grade and less
sensitive to operating costs and initial capital costs.
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Gold Price Sensitivity Analysis
Gold Price
(US$/oz Gold)
Net Cash Flow
(US$M)
After-Tax NPV
@ 5.0% Discount Rate
(US$ M)
IRR
(%)
Payback Period
(years) Payback Multiple
900 -$43.38 -$60.62 - 9.5 0.8
1,100 $66.08 $9.89 6.1% 5.6 1.3
1,300 $176.64 $79.94 12.4% 3.9 1.8
1,500 $286.0 $148.8 17.3% 3.1 2.3
1,700 $395.4 $217.6 21.6% 3.5 2.8
1,900 $505.3 $286.8 25.7% 2.9 3.4
2,100 $614.7 $355.4 29.5% 2.6 3.9
2,300 $724.1 $423.9 33.1% 2.3 4.4
2,500 $833.5 $492.5 36.7% 2.0 4.9
2,700 $942.8 $561.0 40.1% 1.9 5.4
2,900 $1,052.2 $629.6 43.5% 1.8 5.9
3,100 $1,161.6 $698.2 46.8% 1.7 6.4
3,300 $1,270.9 $766.7 50.0% 1.6 6.9
3,500 $1,380.3 $835.3 53.2% 1.5 7.4
3,700 $1,489.66 $903.85 56.3% 1.4 7.9
3,900 $1,599.03 $972.41 59.3% 1.4 8.5
4,100 $1,708.40 $1,040.97 62.3% 1.3 9.0
Figure 3 – Planned Cerro del Gallo Site Layout
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Figure 4 – Cerro del Gallo Process Flow Sheet
Figure 5 – Cerro del Gallo Planned Production Schedule
Next steps
The next steps by Heliostar at Cerro del Gallo will focus on conversion of resources to reserves and additional
resource growth.
This plan includes additional resource and reserve drilling, updating geological interpretations, metallurgical
testing and trade off studies. Positive changes to the gold price have resulted in an increase to the potential
size of the reserve. Additional metallurgical analysis and data points are required on the deposit to support this
increase.
The Company intends to drill with a focus on increasing both mineral resources and reserves and to improve
the geological interpretation for the deposit. Mineralization remains open to the north and at depth. The north
is considered a high potential target for reserve growth but historically was not drilled due to surface access
limitations. The drill density decreases at depth as noted in Figure 2 with in -fill drilling having potential to
improve resource classifications. Further, mineralization is open at depth with potential to expand resources.
Subject to confirming the extent of the mineral resource at Cerro del Gallo, the Company intends to refine the
planned process flowsheet, start preparing permitting and social plans and commence work to prepare a
Ore
Solution
Carbon
Metal/Sludge
Crushing
Agglomeration
Heap Leach
Carbon
Columns
Preg
Pond
Acid
Wash
Strip
Regeneration
Electrowinning Smelting
Dore
ROM
CN-
Recovery
Thickening
Neutralization
Sulfidation
and
Acidification
Copper
Sulfate
Thickening
Filtration
Gypsum
Pond
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feasibility study. Development of Cerro del Gallo is planned after Ana Paula has been commissioned and is in
production.
Mineral Resource Estimates
Mineral Resources for the Cerro del Gallo deposit were updated as part of the 2025 Pre feasibility Study and
are summarized in the accompanying table. The Mineral Resources have an effective date of July 31, 2025, and
are reported on an in-situ basis in accordance with the 2014 Canadian Institute of Mining, Metallurgy and
Petroleum (CIM) Definition Standards for Mineral Resources and Mineral Reserves.
Mineral Resources Statement
Classification Material
Type
NSR
Cutoff
Tonnes
(kt)
Grade Contained Metal
Au g/t Ag g/t Cu% AuEq
g/t
Gold
(koz)
Silver
(koz)
Copper
(t)
AuEq
(koz)
Indicated
Oxide $11.81 10,733 0.41 17.92 0.09 0.60 141 6,184 9,659 207
Mix Oxide $10.66 13,613 0.28 11.12 0.08 0.50 123 4,867 10,890 219
Mix Sulfide $11.81 70,066 0.40 13.70 0.09 0.68 901 30,862 63,060 1,532
Sulfide $11.23 145,572 0.38 13.77 0.11 0.62 1778 64,447 160,129 2,902
Total 239,984 0.38 13.78 0.10 0.63 2,944 106,359 243,739 4,859
Inferred
Oxide $11.81 2,042 0.19 21.08 0.09 0.40 12 1,384 1,838 26
Mix Oxide $10.66 1,604 0.14 16.12 0.07 0.40 7 831 1,123 21
Mix Sulfide $11.81 10,501 0.28 13.75 0.11 0.57 95 4,642 11,552 192
Sulfide $11.23 10,300 0.33 11.74 0.07 0.51 109 3,888 7,210 169
Total 24,448 0.28 13.67 0.09 0.52 224 10,746 21,722 408
Notes to accompany Mineral Resources table:
1. Mineral Resources are reported within a resource shell constrained by the property boundary using the 2014 CIM Definition
Standards.
2. Mineral Resources have an effective date of 31 July 2025. The Qualified Person for the estimate is Mr. Timothy O. Kuhl,
Reg Mem SME and Principal Geologist with Mine Technical Services.
3. An NSR is used for reporting Mineral Resources by material type. NSR cutoffs of $11.81 for Oxide, $10.66 for Mixed Oxide,
$11.81 for Mixed Sulfide and $11.23 for Sulfide were used. The NSR is determined based on estimated processing costs
of US$9.10/t, general and administrative costs of US$0.90t, production taxes and royalty costs of US$1.40/t. Metal prices
of US$2,500/oz Au, US$30.50/oz Ag, and US$4.60/lb Cu were used in calculating the NSR. In addition, a gold recovery of
74%, a silver recovery of 60% and a copper recovery of 17% were used for Oxide material; a gold recovery of 68%, a silver
recovery of 73% and a copper recovery of 62% were used for Mixed Oxide material; a gold recovery of 61%, a silver
recovery of 58% and a copper recovery of 73% were used for Mixed Sulfide material; and a gold recovery of 53%, a silver
recovery of 35% and a copper recovery of 59% were used for Sulfide material in the NSR calculation.
4. Based on the stated metal prices and recoveries, the gold equivalent grades were calculated as AuEq = Au Grade + (((Cu
Price in US$/lb * 22.0462 * Cu Recovery and Payable) / (Au Price in US$/g * Au Recovery and Payable)) * Cu Grade) +
(((Ag Price in US$/g * Ag Recovery and Payable) / (Au Price in US$/g * Au Recovery and Payable)) * Ag Grade). The
average overall payables from the smelter and refineries were estimated at 98.8% for gold, 90.1% for silver, and 88.2% for
copper.
5. Tonnage and grade estimates are in metric units.
6. Mineral Resource tonnage and contained metal have been rounded to reflect the accuracy of the estimate, and numbers
may not add due to rounding.
Mineral Reserve Estimates
Mineral Reserves for the Cerro del Gallo deposit as part of the 2025 Prefeasibility Study have an effective date
of July 31, 2025, are reported at the point of delivery to the leach facility, and are stated in accordance with
the 2014 CIM Definition Standards for Mineral Resources and Mineral Reserves.